For EVERYONE with 32bit Windows:
Try rolling back to 1.7.3 in the Steam beta tab; if that helps then do this Workaround:
1: Open Command Prompt (it's in Accessories in Vista)
2: Set it to be in Admin mode
http://technet.microsoft.com/en-us/library/cc947813(v=ws.10).aspx
3: Paste this in: bcdedit /set increaseuserva 2560
4: Restart
5: If you ever need to undo: BCDEdit /deletevalue increaseuserva
For XP only:
http://www.realitymod.com/forum/f27...ry-errors-allow-applications-use-2gb-ram.html
Note this will NOT help if you have 2gb or less of system memory, only loading fewer DLCs will do that, or rolling back to 1.7.3 .
And please start planning your move to 64bit Windows! Most Windows licenses allow you access to that for free, there's just the procedure of doing a reinstall that's a pain.