Same problem... any idea?
I am experiencing a similar issue when attempting to publish large workbooks. Try rebooting your computer and then try to publish your workbook. Let me know if that works for you (it did for me and it really doesn't make any sense). I am still trying to identify if the problem is a bug or caused by something data related.
If the error persists, look at the log file, which is log.txt within the log folder -- a subdirectory of My Tableau Repository, under the My Documents folder. Copy and post the the lines, starting just before you see the "500" error show up in the log file. Maybe this can provide a clue as to what is causing the error in your case. The "500" error is a very generic error code and not helpful at all as it can be triggered by a number of unrelated factors..