"frozen" VST GUIs in Cubase 5 (32-bit)

A couple plugs (e.g., Expert Sleepers USAMO, MeldaProduction MAnalyzer) load but then show a frozen GUI, i.e., it just captures whatever is in the background at the time and essentially doesn’t work. Cubase itself remains stable when this happens, and it doesn’t seem to be a compatibility issue (these are VST2.4 plugs, all 32-bit).

Anyone encountered this or have any suggestions for how to fix?

here is a photo of what happens:

Photo of glitch added