Since you asked for more info...
URLs left in the Firefix password manager after importing to lastpass:https://secure.ancestry.comhttp://www.blueskyfrog.comhttps://nextelonline.nextel.comhttp://chil.clue.comhttps://www.snort.orghttps://ns.clue.com
examples of URLs that were corrupted or no longer work after importing them into lastpass:
URLs that are IP addresses:http://188.8.131.52/path/to/file
was changed to http://184.108.40.206
(title of main site page) - parens included
URLs that are longer than the domain name:http://www.foo.com/path/to/file
URLs that resolve to pages that use apaches mod_auth style authentication, which presents the user with a pop-up to fill in. I used these URLs and several of the URLs listed above shortly before I installed lastpass and imported to it, and they worked fine. After installing lastpass, I had to go into the vault and edit most of the URLs by hand to remove garbage like (title of site), add in the password, part of the URL, etc.
Since you've decided that this is all my fault for being a stupid user and your software is completely bug free and blamless, let me ask you this:
Before you import from Firefox's password manager, do you do any checks to see if the contents of the file password manager uses are corrupted or are you just hoping that the file is in perfect condition?
During the import process, do you check for duplicate URLs with different passwords, but the same userid?
During the import process, do you check that each field is properly formatted and exists?
Do you have any explanation why the icons the Windows installer put on the system don't work? You kind of ignored that question earlier...