[lunker]

I have a similar problem. Windows 7, Reaper 521pre10 (but it was not new to that pre-release version), S-Gear 64-bit VST.

I have only noticed it with S-Gear, but maybe it's because the size of the S-Gear window can change with different presets (most other VSTs that I use have a constant-size window).

With S-Gear, if I change the preset and the new preset has a smaller window footprint than the previous preset, I get the type of white-space border that @lowellben showed. If the new preset has a larger window footprint then the previous preset, it doesn't display any of the VST that extends beyond the window size boundary of the previous preset. S-Gear has vertical/horizontal scrollbars in the VST if the size of the VST exceeds the FX window size, and when changing to a preset that has a larger window footprint then the previous preset those scroll bars are not displayed (in addition to the window-truncation error mentioned in the previous sentence).

I can fix the window by floating/unfloating the S-Gear VST.

I thought it was a problem with S-Gear, but since someone else is having a similar problem with a different VST, maybe it's not specific to S-Gear.