Thanks for all your minidumps.
Your system always crashed when it was trying to release some memory (from avast and other drivers). Since you're using avast 7.0.1474 for long time and this version wasn't updated from Oct 30 2012, then you should review other lately installed products, OR it's likely that these BSODs are caused by HW fault (memory, cpu overheating, etc). On contrary, all dumps used the same value in CPU registry, so it may exclude random (HW) crashes -- don't you remember when it started and what you installed about that time? You can also uninstall avast for one week to be sure it's not caused by avast.