Could the same thing that causes this warning be causing parallels to crash?
No; this merely indicates Apache is concerned about your Plesk panel SSL cert, generated by Parallels, having a value in the CommonName field which doesn't match the domain name on which you're serving Plesk. This is common to Plesk installs and doesn't cause a problem. The message coincides with Plesk crashes because it's produced each time Apache starts up.
How can I fix it?
Replace the stock cert provided by Parallels with one, perhaps issued by a real CA rather than self-signed, whose CommonName field correctly contains the domain name on which you're serving Plesk. That won't solve the crash issue, though, and it doesn't really matter in any case as TLS will be just as secure either way.