bgl files cause navigation errors

This is the second time I have had this problem - the first is described here (when I thought, I see now probably incorrectly, that this only affected PMDG a/c):http://forums.avsim.net/dcboard.php?az=sho...ing_type=searchI suddenly noticed (this is in FS9.1) that when sat on a runway my ND displays, and also FS Navigator, were showing incorrect information. In other words, if I am on a Rwy 18, which for argument's sake let's say has an exact heading of 180 degs, my instruments and FS Navigator will show a heading of 150 degs. This is a global effect, not just at one particular airport. From my last experience of this, I assumed it was caused by a 'rogue' bgl file somewhere, and sure enough after an hour or so's 'detective work' I tracked the problem down to one small bgl file. Remove it, headings all as they should be. Put it back, problem reoccurs.My question is, how could a bgl file affect the whole of FS like this? I thought if I decompiled it I might see an answer, but none of the tools I have will open it: BGLAnalayze gives me "Error: Compressed BGL file, uncompression failed, file not compressed'. NewBGLAnalyze tells me itr cannot open files of the old type. xmlshell.exe tells me it's not a valid facility data bgl. LWM Viewer won't open it.So a supplementary question is how do I view this file? The file in question is called bsp08_retropro.bgl and comes with a scenery for DAAE (Soummam Airport