Firstly, in defence of loginRadius, I AM using version 3.5 of wordpress and it did say only tested on earlier versions. However, it caused a real headache for me as it locked me out of the dashboard completely, even though it did login to my site, using all of the new buttons. The setting up took a morning to do and relavant buttons linked in with login page, (although the yahoo API had to ne done manually as the provided setup failed)
Support did not answer in a timely fashion (still haven't) and I went to WordPress forums for advise. In the end, I FTP'd into the site and renamed the offending file, which then gave me accees to the dashboard and the plugin automatically deactivated as the renamed file tricked it into thinking the file did not exist. Pity, because clearly a lot of work has gone into the plugin and easy to follow setup procedure . . . but at the end of the day . . . failed big time by denying site admin or dashboard access. Might try again if I have any feedback from LoginRadius support, if not I will not touch them with a barge pole. Especially after reading some of the other reviews . .