[BiO BB] rpsblast error codes

[DGW]

Dear Bio BB list,

I have a rather unusual and technical problem regarding rpsblast. I have 
emailed the NCBI Blast helpdesk, but they have not been able to explain 
yet, so I'm hoping there is someone with some insider knowledge out 
there who could help.

I am using a python script that runs rpsblast for many queries. At each 
call of the rpsblast executable, this script requires that rpsblast 
returns a value of zero to indicate a successful run, before attempting 
to parse the output and move onto the next query. Unfortunately, 
rpsblast doesn't return zero, but returns the value '768', even though 
each search seems to complete perfectly fine. The system being used is a 
Sun OS5 machine. When I test the script on my laptop (Win XP) using the 
precompiled binaries for rpsblast it works just fine.

I can bypass the problem, by just looking for '768' instead of '0', but 
this doesn't bode well for the portability of the script. Also, I am 
curious as to what is causing this to happen.

So, does anyone know what the error values for rpsblast stand for (there 
seems to be no documentation on this)? Are they determined by the source 
code, or by the system the program is compiled on?

Cheers
David