There might be a conflict with this plugin. The only info I was able to get was that when activated with Connections the site broke. I tested both activated with the default 2011 theme and both plugins seems to function correctly. So, it you are having issues, please try deactivating this plugin.
Update: I was told they were unable to login to their admin. I was not able to replicate this issue either.
NOTE: This FAQ was written based on U Comment Extend 1.1.