The problem only happens when the host is in front of the banner (Starts at :17 sec in)... but there is a weird flashing going on, and I have output to various formats (QT, h.264, WMV, FLV) and the problem doesn't go away... not sure what could be causing this...
I have CS5 on PC - I used Magic Bullet Colorista and Looks for the FX
Go back thru the fx you have applied to the clips and see if you can locate the one causing the problem.
I agree with Craig. It looks like the "strobing," that is common with some of the Auto Effects, like Levels, Color, etc., though I have seen similar with a few other Effects.
Good luck, and please let us know about any Effects applied (looked like the background, but I could be wrong).
Also, and if that does not yield anything, I'd look at the Key that you pulled on the hostess, just in case there are some bits of partial Transparency in it.
PS - I watched with rapt interest, due to the wine aspect!