Hard drive writeable but not by file manager

Question

I have a USB HDD that behaves like it is read-only, only in the file manager. I assume it is related to permissions, but it happens with the same file manager in two operating systems.

Setup
The two OSes are Debian Wheezy and Linux Mint, both using KDE so the file manager is Dolphin in both cases. Mint is on a partition of the internal HDD, Debian is on an external HDD. There are two other external USB HDDs from my Windows days. One is NTFS, the other VFAT. This is the mounting information in Debian (my main OS):

/dev/sdb1 on /media/HD_CEIU2 type fuseblk (rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096)

/dev/sdd1 on /media/WDC$USB2 type vfat (rw,nosuid,nodev,relatime,uid=999,gid=999,fmask=0022,dmask=0077,codepage=cp437,iocharset=utf8,shortname=mixed,showexec,utf8,errors=remount-ro,uhelper=udisks)

The problem is only with the VFAT drive; Dolphin has no problems with the NTFS drive. At least in Debian, the VFAT drive is available at bootup but gets initially mounted only after it is requested; the NTFS drive is mounted at bootup (didn't check whether that detail is the same in Mint).

Symptom
The web browser (Firefox), can write to the VFAT drive with no problems. For example, I can download videos. I can also save images via right-click (which is an OS function). In Dolphin, however, trying to drag-and-drop, cut-and-past, or right-click copy or move into the VFAT drive fails, with an error message that it "can't write to <path/filename>".

I believe that this was not a problem until recently but at this point, I can't swear to that. I'm wondering if some recent update might have affected something.

Does anyone have a clue as to what might be going on?

Answer 1

After posting this question, I stumbled onto the answer. I’ll leave the question and post an answer so nobody else with the same problem bruises their forehead smacking it.

The problem had nothing to do with permissions. There were a number of coincidences that pointed in the wrong direction. The files I was trying to move contained a character in the filename that is not allowed in VFAT, the fence character |. There is probably some filename cleanup performed when you save a file directly to VFAT from the Internet (or you would at least get an error message at the time). These had been save to EXT4, where the fence character is fine. Trying to then move the files into VFAT triggered “indigestion”. Cleaning up the filenames solved the problem.