After trying to find a solution on https://forums.comodo.com/leak_testingattacksvulnerability_research/i_fail_dnstesterexe-t18293.0.html
As I dual boot from XP with the x32 version of Comodo, and from Vista x64 with the x64 version of comodo, with same settings on both, I still fail DNS tester on x64 but pass easily on the x32 version. I’m out of ideas. Could this be a bug?