This is really buggin me. Half-Life 2 has become practically unplayable for me in the recent days. While playing, one of these two things happens, especially when the game tries to load the next map:
 
1. This error message appears, then the game exits to Windows.

 
Any idea what that means?
 
2. The game goes back to the main menu, but when I choose an option other than Quit, the dialog box where the options normally appear now looks like this (example below is when I select New Game):
 

 
In a nutshell, all dialog boxes don't work, other than the control box that lets you either move or close it, and the "x" close button. Now this is really puzzling.
 
Any help here? So far only Half-Life 2 is having these problems, while just about all my other games (including Doom3) are problem-free thus far.
 
Current specs:
Pentium4 3.0GHz Prescott w/ Cool Master Aero-4 Lite fan/heatsink
ASUS P4P800-X Motherboard (using onboard sound)
1GB PC3200 SDRAM (AM1 512MB DDR-400 x 2)
ASUS N6600 / GeForce 6600 video card w/ 128MB RAM
Promise SATA150-II IDE/SATA Controller
4 Seagate 7200RPM Hard Disks (1 120GB ATA-100, 1 120GB SATA, 1 160GB ATA-100, 1 200GB SATA)
Sony DRU-710 DVD Burner