I emailed Garmin about this, and here is the reply I got...
Was that card ever used in a cell phone or another mobile device. You may need to reformat the card to FAT32. This should eliminate the issue. Let me know what you find out.
The card has only been used in the Vista and it works with no problem in 2.80, but with 3.00 I can't turn on tracklogs.
So... I bougth a new card (Lexar 2G) and upgraded my Vista HCx to 3.00.
1. Insert blank Lexar card. turn on tracklog. No problem.
2. Copied all the maps and tracks from the old SANDisk card to Lexar. switched tracklog. No problem.
3. Formatted the SANDisk card (blank). Insert. switch tracklog. No problem.
4. Copied the maps and tracks to SANDisk card. switch tracklog. Frozen!
Conclusion. Some combination of map data and SANDisk 2G are not compatible with Vista HCx 3.00.
So my Vista HCx will stay with SW 3.00 and Lexar 2G card.
edit: But the power-off-beep-until-batteries-removed is now every time I power off.
I had to quote myself one more time.. Solved both my problems with a hint from another webpage. Are you all Mac users who have problems? I reformatted my SanDisk card under windows 2000 and copied all garmin files from my other card and omitted spotlight and trashcan files.
Now I can turn on/off tracklog and power off with no beep until batteries are removed. :-)
Maybe the latest firmware is incompatible with Mac format FAT..
If the card is attached under Mac (GPS or card reader) spotlight and trashcanfiles are created and the beep at poweroff returns. The solution is to remove those files under windows again.