Confirming that part of the problem is FAT: after reformatting various USB-sticks with NTFS they were again writable under Ubuntu 10.04. The mystery rermains why and how the use of a Sandisk mp3-player should have created this situation (before that all sticks and SD-card behaved normallly.)
The FAT phenomenom explains too why my external harddisks were unaffected - they are of course formatted with NTFS in order to allow large file sizes.
Confirming that part of the problem is FAT: after reformatting various USB-sticks with NTFS they were again writable under Ubuntu 10.04. The mystery rermains why and how the use of a Sandisk mp3-player should have created this situation (before that all sticks and SD-card behaved normallly.)
The FAT phenomenom explains too why my external harddisks were unaffected - they are of course formatted with NTFS in order to allow large file sizes.