At the VirtualURIMapping node, I incorrectly addedd a New Node Data instead of New Content Node. Then I immediately try to remove the Data node but then the whole server is screwed up and any URL results as error 500. The error is as follows:
java.lang.String cannot be cast to info.magnolia.cms.beans.config.VirtualURIMapping

Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to info.magnolia.cms.beans.config.VirtualURIMapping
at info.magnolia.cms.beans.config.VirtualURIManager.getURIMapping(VirtualURIManager.java:83)
at info.magnolia.cms.filters.VirtualUriFilter.getURIMapping(VirtualUriFilter.java:141)

i tried to repeat the same process in a fresh downloaded Magnolia instance and I could easily repeat it. And OMG there is no way for me to fix as I can't access the admin central anymore.

It is obviously a critical bug to me because a user mistake could f up the whole system unnecessarily. I don't blame the lack of validation in the UI as you guys are working hard to improve the admin ui, but it also show a lack of exception handling. When processing multiple URI mapping rules, if one of the rules fail, it shouldn't cause the whole system to fail. (if it is a security/access control rule, i would accept a single exception in processing the rules to cause a deny access)

p.s. I tried to post to the user-list to look for a way to fix the problem but the mail-list system seems to be broken and there is no reply after i have replied the verification email. Is there ant wat to fix the problem, i.e. is there any way to remove the last "untitled" uri mapping entry without accessing Magnolia (coz all url including JCR browser can't be accessed.)