I keep getting this error when I get right into making my NavMesh. I can normally get about halfway into NavMeshing my interior with no problem, then this comes up:
"NavMesh (01001D22) with 47 Triangles in Cell '111Interior' (01000AF4) has warnings. Please fix before checking it in.'"
Now, typical of the GECK not to actually tell me what I have to "Fix".
While in Navmesh mode, NavMesh > Select Triangle By Index > Check NavMesh > Go To and the render window should focus on the problematic triangle. If what's wrong is not evident by looking at it, removing the triangle and replacing it should clear the reported error. Checking the NAVM as described above should verify it's fixed or point you to the next error if present.