NSIS Error in uninstaller

[MSG]

When I was playing around with the problem in this thread, I ran into something rather strange.

Code:

outfile "d:\test.exe"
page instfiles
UninstPage instfiles

section
writeuninstaller "d:\untest.exe"
sectionend

Section "Uninstall"
MessageBox MB_OK "Working"
SectionEnd

The installer works fine, but the generated uninstaller throws an NSIS Error ("Error launching installer"). Using NSIS 2.46 and NSIS 2.46-Unicode. Can anyone reproduce?


Edit: Moving untest.txt to a d:\subdir, the uninstaller works fine. This could suggest a permissions issue, but what could the uninstaller be trying to do that would lead to a CRC error?
Some details: The Authenticated Users group has everything except Full Control on d:\, while the Users group has only 'read & execute', 'list folder contents' and 'read' access. I'm logged in as a userlevel user.

Another thing I can imagine is a backslashes issue, something like trying and failing to access d:untest.exe.