[OS X TeX] htlatex/gs trouble

[Jan Hegewald]

Dear all,
after using gwtex for a long time, I now switched to MacTeX (LaTeX  
seems to run fine here too (-:). But there are some trouble when  
invoking htlatex:
	System call: convert -trim +repage -density 110x110 -transparent  
'#FFFFFF' zzmuscle_developers_guide.ps muscle_developers_guide0x.png
	Error: /undefined in obj
	Operand stack:
	   4   0
	Execution stack:
	   %interp_exit   .runexec2   --nostringval--   --nostringval--   -- 
nostringval--   2   %stopped_push   --nostringval--   -- 
nostringval--   --nostringval--   false   1   %stopped_push   1905    
1   3   %oparray_pop   1904   1   3   %oparray_pop   --nostringval--    
1888   1   3   %oparray_pop   1771   1   3   %oparray_pop   -- 
nostringval--   %errorexec_pop   .runexec2   --nostringval--   -- 
nostringval--   --nostringval--   2   %stopped_push   --nostringval--
	Dictionary stack:
	   --dict:1155/1684(ro)(G)--   --dict:0/20(G)--   --dict:77/200 
(L)--   --dict:174/300(L)--   --dict:43/200(L)--
	Current allocation mode is local
	Last OS error: 2
	Current file position is 15266
	GPL Ghostscript 8.63: Unrecoverable error, exit code 1

Since I do not use htlatex very often, I am not sure if this problem  
is even related to the MacTeX install. Can anyone point me to where to  
look for the glitch? Is it ghostscript, image magic or htlatex?

Many TIA,
-- Jan