This is the first time I have written on a forum, sorry to jump on your thread nevermind but I am having excatly the same problem with my 16GB micro HCSD.
I use the card non stop with my Nokia N97 and I have never had any problems. I have Music, Movies and Pictures stored on there and regularly change and swap the movies and music on my phone. I also have a dongle attached to my phone so regularly remove the card and use as a flash stick, with absolutely no problems.
2 days ago I deleted a couple of videos, only they weren't fully deleted. The file size of each dropped to 0kb but they could still be seen on my card, plus I lost another video that was in the same file that I didn't want to delete. I tried to access the card but it started locking up my phone, thought it was the handset that was goosed, but as soon as the card is removed the phone is fine. The card also started locking up my computer until removed.
I deleted another file while I was able to access the card on my computer (don't ask me how, just got lucky), the deletion was successful and my card was suddenly freed up, so back in the phone it went. Deleted another picture and I was back to square on. Have been able to copy valuable files off the card to make sure I don't lose them, so I'm now ready to wipe the bloody thing and get it working again.
So far I have tried,
1. Windows, Right Click, Format, Both normal/quick format= same message as nevermind 'unable to complete format'
2. HP USB Disk Storage Format Tool= same as nevermind 'write protected'
3. Active@KillDisk, tried both Wipe=no progess made error message
Killdisk= 100% progression, error meesage right at the end.
4. Manual deletion of files now impossible error message 'file is too deep?' WTF? Its not a swimming pool, just get in there and delete it.
5. I've even had the stupid thing in the freezer (heard it can reset things, but that may be baloney)
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHHHHHHHHHHHHHHHHHHHHHHHHH Its doing my head in now. I've deleted/Formatted but all my stuffs still there and accessible, all be it very very slowly with loads of error messages.
The only thing I haven't tried is formatting in digital camera, but I don't have one and doubt a camera will be able to read 16GB micro card.
Please help and good luck to Nevermind as well, it is very frustrating and they're bloody expensive little things.
PS. Sorry about the long thread.