@slip: I have to admit I am a bit at a loss here… : I cannot reproduce the error (scripts are tested on 2.47 and now I tested it on 2.48 as well, but I haven’t yet installed the official 2.48a version ). Is it possible the script is unpacked improperly? To test if Blender doesn’t know where to find stuff or that there is something wrong with the script, you could try to run the script ‘by hand’, i.e. load it in the texteditor [texteditorwindow]->File->Open, then Alt-P (which runs the script from the textbuffer)
edit: cannot reproduce it on 2.48a (it’s all windows xp 32 bit here)
to see if the script downloaded correctly, you can compare its md5sum: on a complete python installation you can do this:
C:\Python25\Tools\Scripts>python md5sum.py “c:\Temp\add_mesh_gears.py”
(of course your python installation directory might be different, as the location of the downloaded script, but you get the idea, that long hexadecimal string has to be the same as posted here)
I see that since version 2.48a there are some changes/bugfixes relating to python, especially the 64bit versions, committed to SVN, so there might be some issue there although I can’t find any clear comment on that.