That's very strange...
Which dll ? Which Windows do you have ? XP ?
I suggest that you install the latest version of Coollector
above your current install. Don't desinstall anything, just install at the same location. This way you should not lose your personal data, but just in case I recommend that you make a backup copy of your .cool file (should be Coollector\Coollections\MyCoollection.cool).
(backups are always a good idea)
And if after that you still have problems with the update, let me know.