Strange crash while demo playback

[Gian Paolo Mureddu]

I had twice tried to view a demo I created (AS-Mothership) and the game 
simply would exit just after the demo starts to playback (when the 
anouncer says "You are attacking"). The ouput on the log file is quite 
long, so I couldn't say what parts to post, but here's an excerpt:

[LOG]
Log: DemoRecSpectator setplayer SDLViewport
ScriptLog: ## ASGRI::SetupAssaultObjectivePriority
ScriptLog:   Assault Priority: 0 DefensePriority: 101 Info: Destroy 
lower shield generator Destruction: Shield Generator Destroyed
ScriptLog:   Assault Priority: 1 DefensePriority: 100 Info: Destroy 
upper shield generator  Destruction: Shield Generator Destroyed
ScriptLog:   Assault Priority: 1 DefensePriority: 100 Info: Destroy 
upper shield generator  Destruction: Shield Generator Destroyed
ScriptLog:   Assault Priority: 2 DefensePriority: 99 Info: Proceed to 
landing bay Destruction: Attackers have entered the MotherShip!
ScriptLog:   Assault Priority: 3 DefensePriority: 98 Info: Destroy 
energy bypass Destruction: Destroyed energy bypass...
ScriptLog:   Assault Priority: 3 DefensePriority: 98 Info: Destroy 
energy bypass Destruction: Destroyed energy bypass...
ScriptLog:   Assault Priority: 4 DefensePriority: 97 Info: Destroy 
sentinel Destruction: Sentinel destroyed!
ScriptLog:   Assault Priority: 4 DefensePriority: 97 Info: Destroy 
sentinel Destruction: Sentinel destroyed!
ScriptLog:   Assault Priority: 4 DefensePriority: 97 Info: Destroy 
sentinel Destruction: Sentinel destroyed!
ScriptLog:   Assault Priority: 5 DefensePriority: 96 Info: Use panel to 
unlock core hatch Destruction: Hatch lock #2 released!
ScriptLog:   Assault Priority: 5 DefensePriority: 96 Info: Use panel to 
unlock core hatch Destruction: Hatch lock #1 released!
ScriptLog:   Assault Priority: 6 DefensePriority: 95 Info: Destroy the 
conductor Destruction: Conductor destroyed!!!
ScriptLog:   Assault Priority: 6 DefensePriority: 95 Info: Destroy the 
conductor Destruction: Conductor destroyed!!!
Log: Precaching: AS-MotherShip.LevelInfo0
Log: Static mesh batches: 46448676 vertex bytes, 5513508 index bytes
Log: Allocating 65536 byte dynamic vertex buffer.
Log: Allocating 32768 byte dynamic index buffer.
Log: Finished precaching geometry in 6.456 seconds
Log: Finished precaching textures in 4.791 seconds
Warning: DemoRecSpectator AS-MotherShip.DemoRecSpectator (Function 
Engine.PlayerController.ServerShortTimeout:0021) Accessed None 'Game'
Warning: AnnouncerQueueManager AS-MotherShip.AnnouncerQueueManager 
(Function Engine.AnnouncerQueueManager.ProcessQueueItem:005E) Accessed 
None 'myHUD'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4Assault.ASVehicle.DrawHUD:005F) Accessed None 'myHUD'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0036) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0045) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0068) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0077) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:022F) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:023E) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0261) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0270) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:02A1) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:02B0) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:02E2) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:02F1) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0513) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0522) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0554) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0563) 
Accessed None 'H'
Warning: ASVehicle_SpaceFighter_Human 
AS-MotherShip.ASVehicle_SpaceFighter_Human (Function 
UT2k4AssaultFull.ASVehicle_SpaceFighter_Human.DrawWeaponInfo:0582) 
Accessed None 'H'
Critical: Assertion failed: Font [File:UnCanvas.cpp] [Line: 489]
Exit: Executing UObject::StaticShutdownAfterError
Exit: Executing USDLClient::ShutdownAfterError
Log: Waiting for file streaming thread to finish...
Exit: OpenAL Audio subsystem shut down.
Exit: Exiting.
Log: FileManager: Reading 0 GByte 224 MByte 80 KByte 148 Bytes from HD 
took 31.808382 seconds (7.622620 reading, 24.185762 seeking).
Log: FileManager: 0.000000 seconds spent with misc. duties
Uninitialized: Name subsystem shut down
Uninitialized: Log file closed, Wed Oct 13 21:42:55 2004
[/LOG]
What can be causing this?