I did verify the path and filename.
Look at that error message again - it's trying to open "wallet.dat/main". I certainly didn't type in the "/main" - the program somehow added that to the default filename. Make sense?
Yes it's ok, it's a part of code from the original pywallet because main is the database name, and this doesn't change with the actual wallet path (even savingswallet.dat would be labelled in this error as wallet.dat/main).
This error happens when pywallet cant' read the file. Are you sure the file is readable? Try opening notepad and open the path you put in pywallet.
Just to be sure, it's a wallet.dat from the satoshi client, right?