Verification Error; content mismatch

Using an older arduino with ATMEGA8, trying to upload a new sketch using 0010A today I get the error:

avrdude: verification error, first mismatch at byte 0x0000
0x39 != 0x00
avrdude: verification error; content mismatch

any help?

thanks

Did this board work before? When? Has anything changed since?

Did you select the right board from the Tools > Board menu?

the board has worked fine for the last couple years...
My problems started when I tried to reload a sketch which I have used successfully in the past.
I have selected the correct board from the menu.
some of my searching has suggested a bootloader problem?

Thanks for the help

It's hard to tell. It looks like the program's not being successfully written to the board. You might try setting upload.verbose to true in your Arduino preferences file (check the preferences dialog for the location) and then uploading.

A new chip might help, or reburning the bootloader onto the one you have.