can you check in Jira for 2.6.3 or 2.6.4, i remember such an issue but don't remember exactly (it was actually a problem with MySQL and the dashboard)
I do not think it is MySQL specific as it does the same with Hypersonic as DefaultDS and no MySQL present. I checked Jira but I could not find anything related to this problem.
What i meant is that with MySQL it was blowing on the dashboard
I could not find the Jira entry you mentioned.
I tried a fresh install of 2.6.2 and the problem exists on a 'virgin' server.
I downloaded jboss-portal-2.6.3.GA but the issue seems to be fixed. I could not reproduce it. I guess I have to upgrade to 2.6.3.