There are also no events here. I think the lack of a clear button is due to you using an unsupported browser version. Try using Mozilla, and see if the buttons at the bottom show up.
Okay, this alert is buggy anyway since it doesn't contain any events. The only way to clear it at this point is to reinitialize the EPM database with the command:
NMSROOT/bin/perl NMSROOT/bin/dbRestoreOrig.pl dsn=dfmEpm dmprefix=EPM