Installing Flex 3 Issues
After installing Flex 3 form Flex 3 Beta 3 I had lots of issues with keyboard short cuts. I found that some hidden files from the beta were still on my system in ~/Documents/Flex Builder. I was able to solve all issues by changing the name on that directory and reinstalling Flex.
If your having issues and had Flex Beta installed check out these instructions from adobe. The worked for me when upgrading from Beta 2 to Beta 3.