When i trying to open my cubase 6.5 taking long time and also at closing
No details make it tough for anyone to assist but…
Generally speaking these issues are usually related to certain VSTs that give Cubase trouble. You troubleshoot it by systematically removing the VSTs from the Cubase scan folder and place them back in a few at a time until you find which one(s) cause the issue.
There are certain VSTs known to have trouble with Cubase. So again, you might want to list some more detail about your system and software. Maybe someone will respond if they recognize something.
Regards 
Thanks so much for your reply, my system win 7 ,processor intel i3-2120,memory 8 GB, i am using vst waves,antares,
one point, when i delete user>spc>appdata>roaming>steinberg- cubase 6 folder some days opening and closing of cubase 6.5 going fine.