UPDATE, SEE UPDATE BELOW...
We were running two DokuWikis without any problems, then there was a need for new one and I installed the latest DokuWiki.
Note: The new Wiki will be just different subfolder, like web\wiki
All working fine except uploads which gives the "No data uploaded. Disk full?". I've read all the posts regarding permissions and since we have two Wikis already working, there is no need to give IIS process Write-rights. Even though I tried this one.
I just copied all the contents of my non-working Wiki to a USB stick, installed Xampp to Vista 32 and everything works. So it is something to do with IIS.
I've done quite a lot of research with debugging, file comparing etc and what I found out is that when I compared "do=debug" commands everything was the same (except folder name of course) BUT the part with [datadir] etc was different.
Here is a copypaste where it does NOT WORK
[datadir] => E:/web/techsupp/data/pages
[olddir] => E:/web/techsupp/data/attic
[mediadir] => E:/web/techsupp/data/media
[metadir] => E:/web/techsupp/data/meta
[cachedir] => E:/web/techsupp/data/cache
[indexdir] => E:/web/techsupp/data/index
[lockdir] => E:/web/techsupp/data/locks
[tmpdir] => E:/web/techsupp/data/tmp
[changelog] => E:/web/techsupp/data/meta/_dokuwiki.changes
Please note it says "E:/", so with a slash! The other, which is working fine has "E:\" so a backslash!
This is how it should be in Windows environment.
How can this be? I think this is the cause... and many people have had this one.
How to proceed, aka tell dokuwiki to use "E:\web\techsupp" instead of "E:/web/techsupp".
My colleague went through differences between the latest and second latest version and he found out that DokuWiki now has data checking in media.php file, lines 242-246.
What we did is that we uncommented all 4 lines and upload now works.
Hopefully this helps someone. Still some bugs though since it does not work with IIS properly.