I found a tricky way to bypass the nameserver bug.
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Firstly, I create a new dynadot account and pushed the domain1 to the new Dynadot account, then setup the name server of domain2 to ns1.domain1.com ns2.domain1.com.
Then, I pushed domain1 back to the original dynadot account.
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However, I am not sure if above methods will caused other unexpected problems.
Regards,
Kam
[This post has been edited by kam on Oct 18, 2010 4:16am.]