Well see earlier in another thread you had a path wrong I see.
Based on you telling me that safe mode is off I would think you either have a permissions issue because permissions need to be 777 or your path is wrong.
On the importer the grabbing of categories we insert the categories via sql and then create the necessary cat file paths like so
Content visible to verified customers only.
Thats where the directories are created based on the path your telling the program
So if the paths are not created on importing files you should be seeing lots of errors.
Is it just this one category or all categories?
If its just that one category create the necessary directory and reimport.