The possible reasons are as follows.
Collaber 1.1 is basically a server based architecture where as previous versions are purely P2P.
If this is the case, you need to import the account (an empty new account) using Import button on the login dialog.
Comments
I am a new, first-time
I am a new, first-time potential user. none of the above apply. I'm using a mac and cannot log in "invalid password or the file might be corrupted"
where are the installation instructions? not a mention of how to install or where (usually on a mac you just drag to applications to install).