That's usually a matter of cleaning your cache or a bad connection. Try this: In your viewer, go to "avatar" and select "preferences". Go to the "nertwork and files" tab, and on the second tab there (Directories) Open the cache location folder. it will open a folder on your computer. Log out of Opensim. Delete everything in the folder you just openened. Empthy your computer's recucle bin. Log back in to Opensim. You will find that you take a moment to properly rez, but most connection issues to other grid will have been solved and you will also experience less "lag" when moving around. Hope this helps!