im having the exact same problems as the both of u and have no idea how to fix it.u can try using anti rapidshare :
www.gamerpool.ch/page/rapid/
just paste the download page u want to download from into the alotted space.but for me it will usually download till about 40% so it pretty much sucks.
i also have a problem using megaupload.com aswell once the timer runs down and i click to download it will goto a blank page that says 'download expired' or something like that but others can still download the file without any problems.