...
Try this:

#ifdef 1
		DLOG("==== ApproximateChar " << ch << " " << (char)ch << " " << fnt << ", tolerance: " << tolerance);
		DDUMP(ValueTo< Vector<float> >(v));
		GlyphPainter chp;
		chp.move = chp.pos = Null;
		chp.tolerance = tolerance;
		extern HFONT GetWin32Font(Font fnt, int angle);
		GetWin32Font(fnt, 0);
//		PaintCharacter(chp, Pointf(0, 0), ch, fnt);
//		DDUMP(chp.glyph);
//		ASSERT(ValueTo< Vector<float> >(v) == chp.glyph);
#endif

GetWin32Font is called by PaintCharacter and has some caching inside too, maybe that is the one that is causing the trouble. Of course, if calling it fixes the problem, try to comment and uncomment...