We recently upgraded to 2008.1 from 2007.3. We are also now using VS2008 but compiling against the 2.0 framework. After the upgrade to 2008.1 the ultrawebmenu no longer works in Firefox. When I use firebug I get the following errors (4 times) for each menu item I select:
getFirstKbItem(undefined)ScriptResource.ax... (line 2431)
Yes, unfortunately this is correct and I can also reproduce this even in our live samples. Good news is that this is already addressed in our internal build and will be available in the next hotfix. I am not completely sure about our policy to supply internal builds to customers prior to our official hotfix, but you can contact Developer Support and ask them if this is possible.