As the stability of the IVMP Client is not very secure or stable yet whilst in testing phases, I advise you to not attempt to use any sort of game modifications at this current time, if you wish to use mods, please use it on another copy for single player, and once the release version of IVMP is out and all the bugs are dealt with, then I am sure you shall be able to use mods on SP and IVMP.

~Regards
Devin Seville