thanks for posting. Are you using the latest release?

Previous releases did do some drawing in the background (and IIRC I 
also fixed some remains of this in the upcoming RC2) to present a 
refreshed menu when it is being invoked. Since Apple seems to rely on 
Front Row having exclusive access to the graphics system at the time 
it's invoked and no major drawing being done in the background, a 
minimal slow down - or interruption - in the intro animation can occur.

Also, the phenoma is more likely to occur on mobile Macs as well when 
they are running on battery power, since their GPUs are then 
throttled by OS X (I noticed when testing some new stuff in RC2).

Best regards, 
Felix