Excel (and also Word and PP) cannot read from some folder, but can read from another

Hi,
I have some network folder mapped as disk. I have full access to this disk, saving there my Visual Studio projects without problems. But Word, Excel and Powerpoint cannot open files from this disk, when I try to open Excel file, I ALWAYS get message "File is corrupted and cannot be opened". When this file copy to another location (even to another mapped disk), it can be opened without problem. I have another 5 network folders mapped as disks and can open any Office file without problem. There are problems with one disk only. Any ideas?