This has been a problem for several betas, and I seem to remember some other people running into the same issue, so I don't know what's going on.
However, it seems that just as a battle begins (not all battles, it occurs probably 30% of the time), the game will freeze for about 30 seconds, and then resume like normal. When this happens I tend to alt-tab the game to see if there's something going on which would cause the game to lock-up, but when I minimize I get an error from my task-bar "Video display driver stopped responding and has resumed." It's important to note that this only happens with Sins. The other crashes are caused by a mini-dump error and I have yet to figure out how to document it them, because they always close when I have to close Sins via ctrl-alt-delete.
I'm currently running Sins on my Laptop which I purchased through my College. The specs are as follows:
Dell Latitude D820
Windows Vista Ultimate 32-bit (DX10)
Intel Core 2 CPU T7400 @ 2.16GHz (2 CPUs), ~2.2GHz
2 GB RAM
NVIDIA Quadro NVS 120M (GeForce Go 7400 Chipset, ~746MB)
Any solutions? Do the devs know of this problem?