Originally Posted by InstantKarma
Go to Settings > Applications > Manage Applications > Market Updater, and select Clear Data. I had a similar problem about a month ago, and that solved it.
Let us know if that does it for you.
That didn't work for me as I don't have a Market Updater. I did try Market and clearing the cache, this didn't help.
Then I tried Settings > Applications > Manage Applications > Download Manager, and selected Clear Data.
This sorted the problem out
Must have been a partially downloaded file that was breaking things eh?