help describe the problem 7.5.3 does not open a lot of vst
does not open a lot of VST 3 and UAD

cubase 7.5.30 (64bit) , windows 7 service pack 1(64bit) ,Intel core i-73960@3.30 , 16gb, VST64bit

those support help me
I got enough resources on my PC (16 Gb RAM, Intel Core i-73960@3.30) but I get limits when I try open some more plugins in VST 64 bit. Is that because Cubase x64 have some limits for plugins quantity? I counted 63max.(format vst3 64bit)
If not so what I need to do?