After a few minutes of gameplay the game will just disappear and i will be at the desktop with no explanation or error. 

Rig - 

Intel Core i7 920 2.66Ghz, 8MB Cache, 1066Mhz FSB, Quad Core 

Gigabyte GA-EX58-UD5, X58/ICH10R Chipset, 6x DDR3 2000, 2x PCI-E x16, 2x GB LAN, SATAII, RAID 0/1/10, 8 Ch Audio, ATX 

eVGA GeForce GTX260 (675Mhz), 896MB DDR3 (2304Mhz), PCI-E 2.0, Exhaust Cooled, 2x DVI, HDCP, HDTV(Super Clocked Edition) 

Corsair 6GB Kit (3x2GB), PC-12800 (1600MHz) DDR3, Dominator DHX, 7-7-7-20, Triple Channel Kit 

Western Digital 1TB, Caviar Black, SATA-II, 7200RPM, 32MB Cache 

Windows 7 home edition 64bit 

I have The Sims 3 and all the expansion packs. 


Can someone please help?    

Data Execution prevention error? I only say that because ive had games on my PC crash like that, without an error message or anything, and it was the DEP doing its job at the wrong time, that was on Vista of course so maybe its not the same, but its worth looking at.

Check out this thread...
 
 http://forum.thesims3.com/jforum/posts/list/345/10110.page
 Its a large thread, but towards the end I believe they pinpoint DEP as the cause of the issue. Users disabled DEP for the sims, which seems to resolve the problem.
 
Edit: In case you're having trouble disabling DEP, here is an article to get you started...
 
 http://windows7themes.net/disable-windows-data-execution-prevention-in-windows-7-vista.html