A while back I had upgraded Joomla to 1.5.5, and I began to get an invalid token page whenever I attempted to do almost anything in my back end. That problem was resolved fairly quickly, but just after that I noticed that I was also getting a 406 error whenever I made a new post to my forum. Unless I click the return to forum link right away, I am redirected to a white page that says NOT ACCEPTABLE. My post, however, remains intact but the error page is very annoying, and will be confusing to new posters. Has this been encountered before?

Thanks,
Dave