When running the Update-Check on my website, sometimes I get a few:
This happens randomly and for arbitrary plugins.Sorry, a problem has occurred while checking <plugin-name>.
Some quick debugging showed that its caused by a failing Ajax request in plugins/hi_updatecheck/updatecheck.php line 138ff. The failure is caused by the server responding with 500 Internal Server Error. I have not investigated the issue further, but it might be worthwhile to do so, if the same issue occurs also on other websites.