64bit installer not working

hi,
i cant get the 64bit installer to work. whenever i try to run the installer i get the windows installer error:

“This installer package could not be opened. contact the application vender to verify that this is a valid windows installer package.”

i have downloaded the installation package many times and it has never worked. also the md5 checksum doesnt match the checksum for the download given on the download page http://easy-vpn.comodo.com/download.html all i can conclude is that the download file on your server is corrupt.

found a working 64-bit installer http://www.pcworld.com/downloads/file/fid,77093/description.html. although this installer works whenever easy vpn is run it says there is a newer version. the version i have installed is:
COMODO EasyVPN 1, 0, 64783, 50
and i cannot update it to the latest version. this is also true for the 32 bit version that i have installed on some other pcs.