Backup the settings and give that method a try and let us know if it makes any difference.
It's now down to around 15-25 seconds but
added the need to enter a username/password to connect, (even for an Everyone share) - so it got removed, (the last thing I want on LAN night is to be bombarded with: "I can't access that directory!" or "What's the user/password?", when I'm busy trying to get that last enemy in OFDR or CoD-MW2.
It's also not just on initial share listing, if I go into a shared folder and then return to the parent, (\\computername), it'll take the same amount of time to list all the shares again - I thought it would have cached them?
EDIT: Just as a matter of interest, could someone using DOpus on Win7 tell me if the "Share with" context menu works?
Here it works under Explorer but not DOpus but as yet I haven't looked into possible causes.