Friend of mine has the same issue all the time. In his case it's related to JomSocial and JS in conjunction with Flash. Sometimes it happens in other opened tab, but pop-up blocks browser anyway (He uses FF 3.6x for Mac).
I also just installed 2.7.2c - at the moment everything is fine.
Perhaps you shold try some basics: clear cache, clear cookies, restart browser. Test on other browser?
Thanks for the info, however I dont have JomSocial installed. I did clear all the cache I coould remember and find. Nothing. After I click on configeration it takes about 30 secs for the error to show up. If I click on NO in the error window the message goes and comes back 4 times. The the DTRegister configuration settings show up and work (as far as I can tell at this point). Strange.