To see if some TAH are "colliding" between them, you can use "TDCGExplorer"
http://sourceforge.jp/projects/tdcgexplorer/releases/
For the error, if it's not a directx errors, a webcam detection errors (the 4.1 can use them), it's perhaps one of the TAH that not fully compatible with 4.1 (one of the toonshader2.tah version for exemple).
To see if it's a TAH that cause it, I suppose you have already tried to temporary remove them all by putting them in another folder except the base one (
base, base_xp, base_xp1...4 and perhaps the SP one if you have them
base_sp0...2r1), and launch with the ObsDX9.exe that come in the "4.1_nobase".