Just stumbled across this thread after spending literally the whole day trying to figure out why I was getting "Failed to create directory" when attempting the FTP test on my 932L to my new router, a Zyxel VMG8924-B10A. Note that my camera is a 932L, not 933L. Perhaps likely that other, if not all, Dlink cameras have this problem?
As above, unticking the create subfolder option fixes the issue.
BTW, my old router (with USB FTP) was a Thomson Speedtouch 585n which all worked fine. So it appears to not only be specific to Netgear routers!
I also have a Trendnet TV-IP851WIC camera which also suffers the same problem. The layout of the web gui seems rather similar to dlink cameras, I've always suspected some kind of similarity between the two..
Hoping for a camera-wide fix soon..!