Thanks for the bug report, unfortunately I have not been able to reproduce this issue so far. I tested this under Windows XP and Windows 7 using the command "//echo $sfile(*)". The identifier returned the full path and filename of the selected file. I tested this with different files in different folders.
If you test this by copying mirc.exe into an empty folder, creating an empty mirc.ini in that folder, and then running that mirc.exe and using the "//echo $sfile(*)" command, do you still see the same issue?
Also, can you please type the following into your copy of mIRC and report the results:
//echo -a $os $version $beta $md5($mircexe,2) $file($mircexe).sig $script(0) $dll(0) $com(0)