I just got the game in and I was doing a bit of 'Instant Action' gaming.
When I played the map:

ONS-CrossFire

In onslaught mode, after about 5 minutes, I was driving in a tank and bumped
into some other vehicle, the game crashed.

I'm not really able to reproduce the error, this is the output on the commandline:

$ut2004
Exporting ONS-Icarus.....Successful!
WARNING: ALC_EXT_capture is subject to change!
Xlib:  extension "XiG-SUNDRY-NONSTANDARD" missing on display ":0.0".
Resolved ut2004master2.epicgames.com -> 207.135.145.7
Connection established.
ssssssssssAssertion failed: p->model1 [File:KFarfield.cpp] [Line: 937]

History:

Exiting due to error
$

The logfile says this:

Debug: UT2k4MainMenu.Opened()   Sender:None
ScriptLog: Attempting to close a non-existing menu page
Log: URL: Adding default option Name=Player
Log: URL: Adding default option Class=Engine.Pawn
Log: URL: Adding default option Character=Damarus
Log: URL: Adding default option team=255
Log: URL: Adding default option Voice=XGame.AlienMaleVoice
Log: Browse:
ONS-Crossfire?LinkSetup=Default?Game=Onslaught.ONSOnslaughtGame?bAutoNumBots=True?Name=Player?Class=Engine.Pawn?Character=Damarus?team=255?Voice=XGame.AlienMaleVoice
Log: Collecting garbage
Log: Purging garbage
Log: (Karma): Level Karma Terminated.
Log: Garbage: objects: 55795->47331; refs: 613055
Log: Game class is 'ONSOnslaughtGame'
Log: Bringing Level ONS-Crossfire.myLevel up for play (0) appSeconds: 401.267325...
ScriptLog: GameInfo::InitGame : bEnableStatLogging False
ScriptLog: bAutoNumBots: True
ScriptLog: Using Official Link Setup: Default
Log: Spawning new actor for Viewport SDLViewport
Log: SET PLAYER!
ScriptLog: New Player Player id=5e107f8601b4353de31ced2da386771f
Log: Precaching: ONS-Crossfire.LevelInfo0
Log: Static mesh batches: 7036056 vertex bytes, 734370 index bytes
Log: Allocating 32768 byte dynamic index buffer.
Log: Allocating 589524 byte dynamic index buffer.
Log: Allocating 65536 byte dynamic vertex buffer.
Log: Finished precaching geometry in 0.943 seconds
Log: Finished precaching textures in 2.992 seconds
ScriptLog: START MATCH
ScriptLog: NOW!
Warning: Failed to load 'NULL': Can't resolve package name
Warning: Failed to load 'Mesh None.': Can't resolve package name
ScriptLog: Could not load mesh:  For player:
Critical: Assertion failed: p->model1 [File:KFarfield.cpp] [Line: 937]
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 256 MByte 554 KByte 269 Bytes from HD took
12.933992 seconds (6.597446 reading, 6.336546 seeking).
Log: FileManager: 0.000000 seconds spent with misc. duties
Uninitialized: Name subsystem shut down
Uninitialized: Log file closed, Wed Apr  7 13:29:42 2004