I had this strange problem with right click on any file other than .cmd, .exe causing windows explorer to hang for like 45 seconds. After much searching on the web, came across this solution.
I used Reg Scan utility from Nirsoft, searched for registry values beginnning with \\ which denotes network path. Most the registry keys tied to these values where Shell, Open command for some registered file types and classes. When I pinged the IP address or network path, it was not going , so deleted all these entries. Bingo!!! Right click is now faster.
Also, the New menu under the right click context menu was taking some time. Some newly installed programs were causing this issue. If you don't recognize an entry in it, it is better to delete it. You can do this by using Nirsoft's Reg scan utility or shellexview from Nirsoft.