All of the Telerik Upgrades require full read/write access to the web.config file in your root directory - I would start with checking that both the Root and the web.config file itself both had the correct permissions set for your application pool user.

With regard to any actions the involve - JAVASCRIPT - u may need to FORCE a refresh of the cache in your web browser - many browsers seem to cache javascript differently to other web page - as such the old versions seem to get left in the cache more often than not  - especially if you happen to be using chrome.  This includes all the popup/dropdown menu systems among other things.

As for placement of menu layers - this still comes down to z-index and your skin.  DNN has made some changes in the 601 core to handle many of the common issues - but if you skin uses z-index in any way itself then you may still need to alter your skin to be compatible.

Westa