cubase 5 update issue

hello everyone.
i have been trying to update my cubase 5 software to 5.5.0 but have failed till so far.
when i click the update file a meter appears, which finishes, but afterwards, during the folowing step, a small window pops up for a fraction of a second, only to dissapear.
this is as far as i get in the update process.
Kind regards.