[ubuntu] Unable to install a .deb file

This was erroneously marked as solved by an admin so I'm reposting it:

I'm trying to install a 3rd party .deb file. When I double click it, the software center opens and I click the Install button. After doing so, the Insall button then says "Installing...", the progress bar goes quickly over to about 10% and then disappears entirely and then the Install button is just there again to click. It won't install for some reason. If anyone knows a way around this or if I'm doing something wrong, any info would be most appreciated. The deb file in question in this particular case is a file to install a vpn client although I have had the same issue with one other deb file today (to install Opera) since I installed Ubuntu this afteoon.