The Megaupload plugin is currently not working since the checks in checkProblems() check on english error messages, but Megaupload is now delivering a localized version.
Simple downloads work again by commenting out the call to checkProblems() on line 72 in MegauploadRunner.java, that's however just a dirty workaround.
However, just changing
method.setRequestHeader("Accept-Language", "cs,en-us;q=0.7,en;q=0.3");
to
method.setRequestHeader("Accept-Language", "en-us;q=0.7,en;q=0.3");
in DownloadClient.java doesn't seem to help.
Unfortunately I right now don't have much time to further investigate this issue.
(Actually, I have no clue why removing the checkProblems() check solved the issue for me, it only checks whether there
are some error messages on the page, it should not throw an exception if it finds none of them - which makes me unsure about the language again, since other cases like 'Download limit exceeded' get detected properly)
Example File
