Special symbols e.g. the colon, seem to break the filtering system.
For example, in SOM 240 where we have parameters like "20:25" under vmcron, selecting it causes it to reject everything -- resulting in a blank graph. Also, linking to it directly doesn't work either (http://perf/?som=240&v_vmcron=20%3A25), causing it to accept everything -- same behaviour as "ALL".
I believe this has now been fixed.