APPCRASH help needed

[Boatshoes]

I finished building my new rig about 2 days ago and everything has gone fine except for a problem that came about today when trying to play Half Life 2. All my other games work fine (even the other ones that were downloaded from the same Orange Box CD) but for some reason Half Life 2 has had problems. The first night I was able to play HL2 without any problem. I was able to save and load games just fine. For some reason, today I was unable to play HL2. The main menu would come up just like normal but when I would try to load a saved game it would say windows is having a problem and would close it down. The same thing happens when I open up Windows Media Player except with that one I am able to open it back up a second time and no problem arises. Any help on how to disable this function or fix the problem is appreciated.

Running Home Premium 64bit
780i EVGA
xfx 9800gtx
e84000
4gb dominator
Problem Event Name: APPCRASH
Application Name: hl2.exe
Application Version: 0.0.0.0
Application Timestamp: 470c11ae
Fault Module Name: gameui.dll_unloaded
Fault Module Version: 0.0.0.0
Fault Module Timestamp: 487279f5
Exception Code: c0000005
Exception Offset: 28eafc17
OS Version: 6.0.6001.2.1.0.768.3
Locale ID: 1033
Additional Information 1: 59e7
Additional Information 2: 3e7f15455c51eb54bd086092b189a9cb
Additional Information 3: e8de
Additional Information 4: 736edc19bf21062558793bc66c55f147