Just wanted to provide some info on my fix to this problem for those users owners who may have to deal with this. I won't go into a long discussion on the problem and diagnosing it. If you need some background info please reference the following posts.
Toilet connection to black water tank leak. Posted Sep 24, 2007 by Slapshottr
http://irv2.infopop.cc/eve/forums/a/tpc/f/2486094452/m/8921005734
Black Tank Grommets Replaced Posted Nov 18, 2007 by DancinCampers
The problem: Black water tank leak. Black ABS pipe connecting flange to black tank was cut to short.
The fix: Purchased a new flange $5.55 and grommet $7.70 from Lichtsinn Motors 1-800-343-6255. Note the flange part #116644-01-000 3" Female-4 bolt is listed in the Winnebago parts catalog found on line for a 2006 Itasca 38T. Lichtsinn rep said this has been changed to part #024676-01-000 3" Female-2bolt. Recommend staying with a 4 bolt flange because holes holding flange to floor on 2 bolt do not match up.
I ordered a new grommet but did not have to use it because old grommet was in good shape. I believe in the KISS principal Keep It Simple Stupid.
Found a 4 bolt flange at local RV dealer that matched mine the only difference it had threads in it. Purchased 3" ABS male adapter $3.17 and 2 ft section of black ABS pipe for $2.97 at Lowes. Spoke with Winnebago who confirmed pipe has to sit on bottom lip of grommet. The key is an accurate measurement for the length of pipe and smooth cut. Use a PVC saw and you will have no problem. Cut pipe, glued it to male adapter. As recommended by other forum members I used hand soap on bottom of pipe to help it slide into grommet. By not having the flange on I was able to fill black water tank all the way to top of pipe and observe the grommet. I am happy to report no leaks. Screwed flange to male ABS adapter and bolted flange to floor. Replaced flange seal on bottom of toilet which probably should be done anytime you pull the toilet. This flange seal was $3 and change.
Traveling home after dry camping and not having to clean up crap PRICELESS