It wasn't the permissions on sangoma.module which were wrong but the permissions on /etc/wanpipe/global.conf...
(sangoma.module at line 116 tries to write that file)
I wonder why it was not able to write a default configuration there... Even if you don't have a Sangoma card this directory should have been there I believe... Did you play with persmissions on anything under /etc?
Good luck and have a nice day!
Nick