GarageBand has updated to 6.0.2, updating stability throughout the program and addressing support issues regarding projects that are imported from GarageBand for iPad.
From the release notes:
This update improves overall stability and addresses a number of minor issues, including the following:• Support for opening projects imported from GarageBand for iPad. This update is recommended for all GarageBand ’11 users.
The download is available through the Software Update and through Apple’s support page and is a 45.2 MB big download