well not sure if this is the answer any of you are looking for, but i had the same problem with orca. couldnt get it figured out, done all that was posted on here regarding doing the .htaccess edit, that didnt do anything except display the source code. if that line was not on the htaccess, then i was prompted to download the php4 file.
well my last resort was to troubleshoot some files. i have not got everything done that i set out to do, but this will work and hopefully you wont have any problems see more out of it. i took the orca folder from v6.0.0003 and uploaded it over on the server overwriting the orca folder installed on v6.0.0005. this is most likely a temporary fix, but it certainly worked out for me.
well my last resort was to troubleshoot some files. i have not got everything done that i set out to do, but this will work and hopefully you wont have any problems see more