As of v1.11.12, virtually all conflicts should be resolved. Please let me know if you find any additional add-ons that cause Blank Canvas Gmail Signatures to break.

• Better Gmail 2 - BG Gmail Sigs seems to clash with Better GMail2 skins, specifically the dark skin. The address, subject, and compose windows go over-sized whenever you click on the compose signature button, and the save signature button, as well as other info at the bottom of the compose screen are hidden by the over-sized message body box. Enlarging and shrinking the window contents doesn't help. This happens with 100% consistency. The only fix found so far is to un-check the Skins option in Better Gmail2 add-on, compose the signature properly in this add-on, then recheck the  the dark skin.
  
  
• Google Preview - Some people have reported that disabling this add-on has fixed problems they were having with the Blank Canvas Gmail Signatures add-on. It worked fine for me with no problems for a while (v3.12) and then suddenly started causing problems. I disabled it and BC Gmail Sigs works again. Try using BetterSearch instead.