There are several reasons.
One is the format of the versions number on the original name servers. They used a single digit for the last set where you used the proper two digit format. This means that the original servers report a different version as authoritative than the two new one.
The second problem is that your serial number is malformed. The correct format is YYYMMDD with a two digit update sequence that runs from 00 to 99 added to the end. For the first change made yesterday the serial number should be 2006122401. The serial number you have points to something changed in September of 2005.
In addition, the original servers do not have the two new nameservers listed.
The reason that an MX record is needed is that queries to a nameserver should be able to return all DNS records, including the address of a mail server if it exists.
Aslan is not a
Tame Lion