I was updating a web site for a client and it appeared after I changed editors. I removed CK Editor (which doesn't get along with DT Register) and replaced it with JCE 2.0.2. I don't have JomSocial.
I opened an article to check it, then went to DT Register configuration and saw the same error message.
An earlier version of JCE (on another web site) seemed to completely mess up DT Register so I uninstalled it. This version appears to work, but displays the red warning "Model class JomsocialModel not found in file."
If anyone knows what's causing it (or an ideal editor that plays well with everything), please post!
ernie - yes, get rid of CK Editor. Not just a problem with DT Register... it is just not as friendly as JCE.
The warning you are seeing has nothing to do with the editor though actually. It's a little "bug" that has been addressed. It actually doesn't hurt anything, just looks bad. Download the latest DT Register package (just updated with this fix) and you'll be set. Reinstall... but if you were already running 2.7.7a, then you can also just manually replace this file: