TUAW posted a news story that Apple has released iLife '11 Software Updates

iLife '11 users -- fire up Software Update, as updates to GarageBand and iMovie have just appeared.
The GarageBand update to version 6.0.1 weighs in at 42.7 MB in size, improves stability, and:

Fixes an issue related to undoing Flex Time edits
Removes occasional latency that can occur on guitar tracks
Restores ability to use the Quantize Note Timing menu for tracks with Groove Matching

  iLife '11 Software Updates: GarageBand, iMovie