I also had trouble trying ring games after doing well in ST SnGs. Still haven't ventured back yet, but I am reviewing my play and I think I've figured out where my bad plays were coming from.

Thought I'd point out the things I failed at in case you see some familiarity.
1. Assuming most of my opponents are fish. You have to play opponents as innocent until proven guilty. And even then I think it is safer to wait until they have been proven guilty at least 2 times before adjusting your play to them because of advertising.

2. Getting impatient. If you are used to playing SnG's, you've got thick burn scars on your butt hole because of the fire that is constantly lit under it. SnG's are games of constant survival and punctuated, targetted aggression. Don't sit at a full $25 NL table and after 30 minutes get into the "oh my god I've got to double my stack soon" mode - there's no need for extreme LAgginess or heavy blind stealing.

3. Table selection. SnG's you don't really have much say in who your opponents are. Ring games you do, and that's an opportunity to not forget about.

4. Multitabling is overrated. First and foremost you need to build your reading strengths and know your opponents. Ring games take as much concentration as SnGs, yet most people don't do 2 SnGs at a time. So why 4 table rings? Cut it down to 1 or 2 and see how it goes.