[nznog] global-gateway.net.nz and possible MTU problems

We've got a client in Thailand who is having having trouble with traffic from a number of sites - all of which go through global-gateway.net.nz. Based on the symptoms I'm guessing it may be an MTU issue (along with the other end blocking ICMP) - anyone seen this with global-gateway.net.nz before? If anyone here is responsible for that network I'd appreciate it if you could contact me off-list. Thanks, Scott.