[c-nsp] Ping pattern

[Case Hugo]

We have a customer tied into our Cisco 3550 ---- AP Radio ---  CPE Radio ----- Nortel 1750

When I ping the cpe radio I get a steady flow of 2-6 ms pings.  No time-outs
When I ping the Nortel we get 5 replies of 2-6 ms followed by 2-3 time-outs then 5 replies (2-6 ms) followed again by 2-3 time-outs.  This pattern has been repeating for almost 15 minutes now.

What could be causing this?

TIA