It's just a copy-paste error. In your parameter file, you have an "IMPROPER" section, then a "CMAP" section, and then a bunch of loose improper definitions that CHARMM cannot process because they're in the CMAP section...
Thanks.
I moved the IMPROPERS from NA out of the CMAP section to the "IMPROPER" section.
The other error
PARRDR> NOTE: atom type "HT " is removed from previous group
PARRDR> NOTE: atom type "OT " is removed from previous group
[...]
***** LEVEL -3 WARNING FROM <PARRDR> *****
***** Null nonbond group found. Redo.
******************************************
was due to a double definition of OT and HT in the "NONBONDED" section.
Now it works.
It probably would have taken you less time to analyze the error message and find the problem by yourself than to dump all this stuff on the CHARMM forums. Not to mention the time <b>we</b> would have saved, and the missed opportunity to practice your problem-solving skills. More on that topic in <a href="http://www.charmm.org/ubbthreads-7-5-5/ubbthreads.php?ubb=showflat&Number=24361#Post24361">my problem solving 101 rant</a>.
You can keep your holy-than-Thou attitude... since this is not the only thing I have to worry about. And frankly said, when processing several thousand lines of code/text a day I might miss a line even by a second and third review. And since I never got this kind of "oh so clear error message" I gave up at some point. Sorry I am a human _error_prone_ being.
Anyway, thanks again for your help.
kind regards
Bjoern