Vray loses materials upon reopening SU-2015 64 bit

[alotha]

hi, i am using SU-2015 64 bit win-8 and Vray adv_20025244. my problem is that the vray DIFFUSE MAP(texture) path gets changed automatically for every vismat material thats used in the scene every time i reopen the file. also when i render a surface with vismat materials applied on it, it stretches randomly. please help.