PLEASE HELP!!! UT2003 error, I cant fix it!

[legacy-G4Xtreme]

PLEASE HELP!!!
I have this error whenever I start UT2003...

UT2003 Build UT2003_Build_[2003-04-07_17.42]

OS: Windows XP 5.1 (Build: 2600)
CPU: GenuineIntel Unknown processor @ 2408 MHz with 255MB RAM
Video: No Video

Assertion failed: sizeof(*this)==GetClass()->GetPropertiesSize() [File:UnGame.cpp] [Line: 144]

History: UGameEngine::Init <- InitEngine



I have done everything I can to fix it and it wont help! if someone could PLEASE help me I would greatly appreciate it!!
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My System Spec:
Windows XP Pro with SP1
Pentium4 2.4GHz
ASUS P4PE Mobo
256mb RAM
40GB HDD (7,200RPM)
Geforce4 Ti4200-8X / 64mb
DirectX 8.1b
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[legacy-petey247]

Have you tried going into UT2003 Safe Mode?

[legacy-G4Xtreme]

I am now experiencing a new problem with UT2003. when I start UT2003 I get this messege (the XP 'dont send' and 'send' one) that says: "UT2003.exe has encounted a problem and needs to close. sorry for and inconvenience." Can somebody help me fix this problem please.