Dont ask me how, but i have seen this in all types of windows applications, under some set of conditions the path of executing applications (and other such paths) have been shown as short filenames, I beleive this is a OS problem rather than mircs. I think mirc is likely just pulling its $mircdir value from the os at some point, and for what ever reason it is being handed to mirc as a short filename.
A simple example, assuming your the Administrator (if not substitute your username in)
Copy MIRC.EXE into C:\Documents and Settings\Administrator
Do a dos drop into C:\Documents and Settings\Administrator (start>run>cmd>ok)
Then in the dos drop at "C:\Documents and Settings\Administrator>" type in MIRC.EXE
Then in mirc type //echo -a $mircdir
C:\Documents and Settings\Administrator\
Exit mirc, and back in the dos drop type EDIT, then alt-f and x to exit it
Dos drop becomes "C:\DOCUME~1\ADMINI~1>"
Then in the dos drop at "C:\DOCUME~1\ADMINI~1>" type in MIRC.EXE
Then in mirc type //echo -a $mircdir
C:\DOCUME~1\ADMINI~1\
* see mirc is just returning the the mirc dir as it is defined by the OS
* solution is $+($longfn($mircdir),\) this produces the longfilename (and adds the ending \) nop matter if it was long or short.
