i think part of the strangeness that rootboy's referring to is that, while it is true that mirc won't /write to global.any_extension - if you do:
/write global.hash.txt test
you can go out to win-explorer and see that the file actually *DID* get created. However 6.34 tells you that
//echo -a $isfile(global.hash.txt)
is $false instead of $true
Perhaps $isfile is parsing the filename differently than /write is.
In case it helps track down the peculiarity, 6.32, 6.33 and 6.34 all allow writing to global.hash.txt, but 6.33 incorrectly gave a false message that it failed to write to the file, even though all 3 versions can.