HP-41C Shows 12 Commas, Otherwise Unresponsive

[quoner]

I have an HP-41C that I haven't used for a while. With the old batteries, it wouldn't turn on. I installed new batteries, and now it displays a string of 12 commas like this:

,,,,,,,,,,,,

The calculator is otherwise unresponsive to all key presses. I can't even turn it off. Is this unit completely dead? Is it repairable? Thanks.