Graphics freeze momentarily every second

[Cantoris]

Loved this game and played it successfully in the past.

A couple of months later I'm back to try some user-made levels and now have problems. Don't know whether this is due to Dark Descent updates, new graphics drivers, windows updates or something else.

Basically, there is a tiny freeze about once a second all the time during the game - including at the menu screen. It affects the mouse too. It makes the game pretty unplayable.

I've tried reducing various settings, turning off Aero, closing various other apps, disabling antivirus etc.

One custom game I tried kept crashing at the same point early on claiming my graphics card wasn't up to the job (an Nvidia pop-up on the desktop).

OS = Windows 7 64-bit SP1
CPU = Core2Duo E6420
RAM = 4GB
Graphics card = Nvidia 7600GT
Sound Card = Creative Labs X-Fi Titanium

Graphics drivers are the current Nvidia ones (I uninstalled the old ones before putting the new ones on).

Windows Experience Index:
CPU = 5.3, RAM = 5.5, GFX = 5.7, Gaming GFX = 4.3, HDD = 5.8

Thanks for any suggestions.