How did you go about upgrading to Leopard? http://www.gnutellaforums.com/genera...sx-10-5-a.html

After doing any system updates, make sure you safe boot and repair permissions.

It may be worth making a note of all your LW settings, then deleting the LW prefs folder, thus getting fresh ones next time you open LW; Deleting LW Preferences folder in OSX

It may also be worth doing a bit of a clean out of old incomplete files: Tip: Purge the Downloads Queue! (click on blue link) as this will make a big difference to performance. There may also be some fakes in there which are giving LW hell attempting to find and connect to.

Keep your shares not much above 2,000 or less if large files.

If still problems, go to LW's preferences options > Advanced > Performance & disable all options on that page.