Well,, I set my viewer to film strip, went into my keyboard shortcuts and made sure it was (option +command + V) and the viewer comes up with a film strip and same thing when I try to hide it.. Also with option+ command + B,,hiding browser I have not problem retaining the filmstrip mode..
I think there is an issue with your settings...do you have it set viewer mode to primary?
Also make sure your set to filmstrip mode..i remember having this type of issue but dont really remember the solution yet..