Thanks to those who suggested that as a solution.
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After installing the Cubase 6.5 update on February 29, I found it's very, very, very slow to startup. On about the third time I started it after installation on March 1 it took about 5 minutes before I got to the project setup window. The initial startup with the VST3 and VST 2.x plugin scans also took a long time, but that's to be expected. I haven't added any plugins though I did install PreSonus Studio One version 2 64-bit since I last started Cubase 6.5.
It seems to hang on the VST 2.x plugin scan. The startup now is actually much slower than the Cubase 6 startup. Anybody else experiencing this? Could this be a leap year bug?

I'm running Windows Home Premium 64-bit with Cubase 6.5 64-bit only. 8GB of RAM and plenty of drive space with a Roland Quad-Capture USB audio card. All drivers are up to date.