First: you really shouldn't have space there. Should be
Code:
-mprecomp:v+srep+lzma:a1:mfbt4:d256m:fb128:mc1000:lc8
Second: maybe it's silly question, but... did you copy also
packjpg_dll.dll and
zlib1.dll?
Third: maybe it's another one... your precomp file is named
precomp.exe or
precomp042.exe, because in reference to your
arc.ini it should has this second name