To everybody; one of the best online diagnostic tool http://www.intodns.com/nawilliams.com1. this tool didn't find the error mentioned, and while it's very hard to detect this problem, posting this address here just wouldn't help.
FWIW, to find DNS inconsistencies you need a full-traversal DNS checker like:
http://www.squish.net/dnscheck Anthony -- www.fonant.com - Quality web sites
