Okay, I got this kind of error message again.  This time I know exactly what I
was doing when it happened.  By the way, it happened on Mac OS X, this time.

What I was doing was running tailor to do "darcs record" in a repo, named
"tailored" at the same time that I ran a "darcs get" in another repo, named "dw"
to get a copy of tailored.  The result was that when I used "dw", I got this
message:

{{{
HACO wonwin-mcbrootles-computer:~/playground/libcurl/dw$ darcs check
                                                           
darcs failed:  Couldn't fetch
`0000081564-08e2f575191165b8d044792021e00a786951b7f770add74aa2a5f01c59b7f581'
in subdir pristine.hashed from sources:

thisrepo:/Users/wonwinmcbrootles/playground/libcurl/dw
repo:/Users/wonwinmcbrootles/playground/libcurl/tailored
cache:/Users/wonwinmcbrootles/.darcs/cache
}}}

Note that I *did* have a global cache in use.  Perhaps the darcs locking doesn't
correctly control simultaneous readers and writers into the global cache?

This is with a current darcs-2:

HACO wonwin-mcbrootles-computer:~/playground/libcurl/dw$ darcs --version
2.0.0 (2.0.0 (+ 220 patches))