I am running Ubuntu 12.04 on a HP box. Approximately two weeks ago for no apparent reason hotplugging ceased to function. No longer did an icon pop up on the sidebar announcing a USB flash memory or the presence of a DVD in the internal dvd drive.
The system is aware of the media. I know this because dmesg messages say so, as does the use of sudo fdisk -l. This shows the partitios on the flash drive. They are not mounted, however. But, they can be. If I issue a mount command the flash drive will be mounted appropriately to the filesystem and I can read/write to the flash.
So, in short, hotplugging just has quit working. Oh, BTW, I can use a udev script to announce the plugging in event. So, no idea what's going on here.
The media themselves are working correctly. I tested this by plugging into a different ubuntu box and hotplugging worked flawlessly.
I also posted this question on the Ubuntu forums and have gotten no response. If this is not the right place to ask the question, I'd be grateful if you could suggest an alternative.