I just changed the vtp domain name on a 3750 switch that was in client mode.
Now I cannot login to the swich and the upstream swich only shows vlan 1 as not pruned on the link!
Changing the domain name should not cause anything to chage should it?
You have probably VTP Pruning activated in your VTP domain. Is that so?
If yes then you've run into an unpleasant situation. For VTP Pruning to work properly, two switches on a trunk link must be in the same VTP domain to properly advertise the VTP Join packets that contains the list of used and unused VLANs. If a device does not send VTP Join packets, or if these VTP Join packets are considered invalid, the device on the opposite side of the trunk link assumes that no VLANs are used at the other end and it will prune all VLANs from that trunk.
This is probably what happened to you. On a single trunk link, there are two switches in different VTP domains. They send VTP Join packets but they mutually ignore them because each one is originated in a different VTP domain. As a result, none of the two switches accepts the information about active VLANs at the other end, and both switches are pruning the VLANs off that trunk.
The solution is to prevent the switches from pruning VLANs on that particular trunk using the command switchport trunk pruning vlan none on both sides of the trunk link. Unfortunately, if you cannot remotely access the switch stack you will have to enter this command from the console of the switch stack.