During the past week the first two only were reported on Windows 8.1, and the third one 99% on Windows 8 and 8.1. It definitely appears to be something platform specific. In the comments other users submitted for these "crash signatures," there were several references to the Norton Toolbar/Vault/Identity Safe/Password Manager being used immediately before the crash. I notice you have some Norton extensions. Could you run LiveUpdate to make sure those are as current as possible, and keep track of whether you notice any association with the crashes? (There might also be information or a workaround on Symantec's support forums; I didn't run that search.)