I have a Virtuemart 1.1.7a install on Joomla 1.5. We're using a Joomla menu as the shop side menu. Not every category is listed in this menu (only the 'parent' categories, no subcategories). When users navigate to a sub category (i.e one not in the list) it highlights the wrong category from the side menu. You can see this on:
http://www.lochlomond-trossachs.org/books.html
and selecting 'Local Authors'. Then menu item 'Postcards' is highlighted on the left.
It would be preferable to either a) highlight no category or b) highlight 'Books' (which is the parent category of 'Local Authors').
I've had a look on the VM forums and web at large for issues with Joomla menus in VM, but the vast majority of results relate to an earlier problem regarding Itemids loading the wrong products ,but this is not the case here. Simply fixing the highlight would suffice!
Turns out using Joomla menus for VM categories just doesn't really work that well. Replaced Joomla menu with VM menu (i.e. mod_virtuemart), and styled to suit.