Ipsec stalling

OpenBSD 3.4 Generic

Greets

I have a scenario that is weird to say the least.

I have numerous IPsec connected networks running
and they run very well indeed. I do have however
1 particular network that started "stalling" every
11 - 12 minutes. It doesn't die, it simply seems to 
stall out and then carry on. When working on the 
system it seems to pulse.( quite annoying actually )

It doesn't matter the time of day or night.

With the exception of IP and password, all the networks
I run are identical in setup, and every other one is fine.

It is inside the tunnel that this primarily occurs and normally 
on one particular end. It does however show itself in identical 
fashion on the other tunneled end although less frequently. Even 
less frequently the pattern shows itself on the public IP side, 
When both ends of the tunnel are on the 11 minute stall cycle 
they do NOT always happen at the same time, they can be approx. 
1 - 2 minutes apart.

The stall lasts for very close to 30 seconds and then the network 
continues fine. As mentioned, this pattern repeats itself.

I have changed the Check-interval incrementally from 600 down 
to 3 seconds with no effect.

It seems to me that this is a service provider issue, unless 
there are some additional timings that I can change but am unaware of.

Anyone seen something like this, or have any setting recommendations?

Sincerely

Bob DeBolt