SYSTEM returns -1?

[srt@aerospace.aero.org]

I'm currently using KCL 1.530 on a Sun 4/160.  Sporadically, my lisp
begins returning -1 to all SYSTEM calls, preventing me from compiling,
etc.  There's nothing wrong with the underlying box in these cases - 
I can still do the "cc" by hand, for instance.  I took a brief look
at the code at unixsys.c but couldn't discern what might be going
on.  Has anyone else had this problem?  Or have any idea what might
be causing it?

					-- Soctt Turner