Windows Explorer - Problem creating new folder

[Reverend]

Have you tried it the other way,(In Windows explorer go to File > New > Folder),or do you get the same problem ?

[wykis]

Try Using Command Line ( Start->Run->CMD->press Enter).
When You Are On CMD Line, select Folder where you want to create new folder in by "cd C:\<folder>" and then press Enter.
After That Write "MKDIR <dir name>" .
If You Need Any Info About CMD Line Functions, Just Write Help