Do a un-install, delete ALL the remaining stuff from the install directory, delete the .set file from the User Files Folder in Documents, then re-install and play the game WITHOUT mods and see if the problem persists-if it doesn't, then the mods were the problem...
If you have V1, update to the V1.01 official patch, as it has a lot of bug fixes...If V2 or V3, you have the latest fixes already installed...
Also note that this section is for UN-MODDED games ONLY, Modding questions go in the Modding Forums, as noted at the top of EVERY section and sub section here, where the underlined words take you to the modding forums..Just a friendly heads up..