It is not a switch. iStripper is simply the new name of the software. Your Virtuagirl account is now your iStripper account. Same user name. Same password. All your cards from vg will play of iStripper. When updated from the old software to the new, it just worked. I did not have to do anything except learn how the new software works.
If you are having trouble post a screen shot of what you see when you run the software.
Along the top you should see a gear wheel icon. Click on it and you go to settings. At the top id a check box for "Advanced settings". Check it. Three box should appear. Synchronize with servers; Register again; and Rebuild collection. If you really have a problem one of these will probably fix it. But it's more likely that the interface just seems alien and you aren't working it right.