Newly purchased iMac with iMove 11 installed.

It keeps telling me I need to update iMovie, but when I try to update it comes up with a drop down field that says "You have updates available for other accounts. Sign in to to your XXXXXXXXX account to update applications for that account. When I signed into the acount it keeps coming back with this drop down field. I am perplexed as to why it won't let me update the newest version of iMovie. Can anyone give me a an idea why this is happening?