Downloaded trials not installing

I am trying to install my legally owned Adobe Creative Suite 5.5 Production Premium on a new machine and I get:

'"Install" can't be opened.  You should eject the disk image.'

This seems to be a constant on the forums, and the only solution is to download.  Unfortunately, this is the 3rd or 4th time downloading and I am getting frustrated.  It appears the only problem is the certificate for installing is incorrect.  Is there any work around?  I am very good with terminal, is there something I can do to ensure the certificate is OK or repair it?  Thanks if nobody tells me to re-download again!