Agreed with the above poster.
You may also find that your apps have accumulated huge caches, and you can resolve your issue (temporaily at least) by clearing them out. Go to Settings > Manage apps, sellect "All," and then press the Menu button. There will be an option to "Sort by size." This will place the largest resource users at the top of the list. Try clearing cache on the top 10 or so and see if it helps.