How to troubleshoot Mist

Could anyone help or point me to some documentation about how to troubleshoot Mist on Windows? (0.8.9) For example, what error messages mean, or what to try if it's not downloading blocks, etc. I perused the Github site and Googled a bit, but didn't find a definite match for my issue.

I'm new to Ethereum in general, but I installed the Mist wallet a week or so ago, it appeared to work, downloading blocks, and kept current for about a day. But now it doesn't seem to be downloading anything and it's about 6 days out. I've restarted, I see peers connected (although not as many as I once did when it worked), but nothing else is happening. In the log I see three error messages. ( #1 Synchronisation failed: block header download canceled (requested) # 2 Synchronisation failed: header processing canceled (requested) # 3 Synchronisation failed: block download canceled (requested))

Also, how exactly would I backup and restore this wallet? I'm assuming Accounts --> Backup --> Accounts for backing up, but I noticed an option for backing up Application Data too, so I wasn't completely sure.

Any help or guidance would be appreciated.