I'm having the same problem but with the portable version.
I can't seem to locate the block_headers file to delete it. I found one but it appears to be from the installed version because deleting it had no affect on the behavior of the portable version.
FYI I use the portable version because the installed version just won't connect to a server no matter what I do.
It should be in the USB stick or in the same directory as the executable as it is portable
I have it running in a tmp directory and I can't find the file. Strange!