Spring RTS Engine

If I have Shadows enabled in the settings, and ANYONE builds a sheild in game, Spring will crash.

First, the computer will lock up totally (mouse+keyboard freezes, music in winamp starts skipping) for about a second, then the computer will start working again, but Spring responds really really laggy. Then after a fe seconds of this, Spring will crash, saying 'Runtime error: Abnormal Program Termination' before quitting. The computer works fine after that, I can start Spring and play a game again, but if another shield is build it crashes again.

Turning shadows off fixes it, but I want shadows :'(

Specs:
Pentium 4 2.40GHz
512mb ram
nVidia 6600GT graphics card

No crash report thingie?

Nope, just this message box. It appears twice, as soon as I cancel one of them another appears.

With shield you mean anti-plasma shield?

Yea, those big bubble shields on some units.

Also, in those few seconds when Spring is lagging before it crashes, shadows for everything appear bugged, flickering on and off over random bits of terrain as you move the camera.