We had a great long term campaign in Kalamar back in '98-99. After it was over, we had trouble getting started in different settings - we tried the Realms, Dragonlance, Ravenloft, a couple of DM homebrews, the Conan world, a brief foray into an ancient Greek type campaign, etc. We also played another fantasy sytem... We just couldn't get going again. Finally, what ended up doing was going back to Basic D&D and running through the Keep on the Borderlands (everybody but my halfling got killed by some sort of ooze or something...) I am sure we had runs of Cthulu and some dark future type games in there as well. What finally worked for us was before 3E came out, we said we are going to have one last short term 2E campaign. It would only last 6-8 weeks at the most. However, with an end in sight, we were able to focus on working together instead of getting in the rut of thinking what is coming 6 months down the road and what NWPs would be best served when my PC is at a higher level. And, we got back into working as a team, having fun, etc.