Can library files not in use cause crashing?

[Ilwrath]

Can a something.library file actually cause a crash even if it isn't in use?

Well, I hate to be like Bill Clinton... But that depends on your definition of "cause" and of "in use."  

The presence of a library in LIBS: may be queried by a certain program, even if it doesn't plan on using it.  IIRC, several CD32 games queried the existance of lowlevel.library, without actually using it.  If it found a lowlevel.library, the game would assume it was on a CD32, and might crash an A1200.  Thus, a library not in use COULD cause a crash of a badly written app.  I suggest digging around with SnoopDOS to figure out what is really happening.  :-)

[Ilwrath]

It's a A4k CSPPC w/OS3.9. The problem is it is even crashing on startup before even launching any programs sometimes. Other times it will wotk for a while.

Ick....  That does sound hardware-ish, doesn't it?

I might suggest cold-booting the system up into 3.1 from floppy/zip, or some other media, to make sure, though.  The 040/060 libs are called by Setpatch, and an improper version (or corruption) of one of these libs can trash a system fairly early in startup.  Also, the ROM update file could cause errors that look like hardware faults.  I actually had a partially corrupted Boing Bag 2 install (OS3.9) cause Yellow-Screen boot faults on my A4000!  

[Ilwrath]

Out of curiosity, do lib files get loaded into RAM in startup or do the lay unused in LIBS until a program calls for it?

As I understand it, they typically would lay unused until a program calls for them.  But, of course, some are going to get called for VERY early in the computer's startup.  Setpatch, for instance, calls at least the 68040.library/68060.library libs, and probably others...  and it should be the first line of your startup.  ;-)  And the ROM update file can be sneaky.  It MAY still load even if you boot with both mouse buttons held and boot no startup.  (I forget if it does, or if it just tacks itself onto a vector and stays around until power-off.  I just remember it being a pest, if it malfunctions!!)