Crash on the second level

[AFnord]

I'm having a strange issue. No, the game does not specifically crash on level 2, but rather it crashes whenever I play my second level for the session. So if I finish level 1, then level 2 will crash, and I'll have to restart the game. If I finish level 2, then level 3 will crash, and I have to restart the game (and so on). I'm still running XP (SP3), and I have an old GeForce 7600GT graphics card (up to date drivers). Any idea what the issue might be?