900mhz traffic drops, but ping don't

I have an issue with a 900MHZ link. Here is some detail.

The link is .6 miles. I have a 333 board on one end, and a 411 board on
the CPE end. There are two clients associated to the AP. Only one is having
the problem (me). Both are in the lower -70’s with upper 90 some percent
overall ccq. The 900 MHZ ap is hooked into the Mikrotik router doing all the
routing. All 3 units are SR9 cards.

The problem is this. I will be going along and I will get disconnected
from AOL IM, ssh, e-mail will stop if it’s checking, pretty much everything
will stop. However pings do not stop. The radio does not disassociate. If I
am pinging the AP it won’t stop either. However, If I have winbox open to
the AP it will drop.

I have swapped out the CPE end thinking it might be a hardware issue.
Like I said the other client on this AP does not see this issue so it is not
the provider, doubtful it is the AP. After I swapped out the CPE from a 333
to a 411 board my ping times to the AP (directly connected) went from 1-2ms
to under a millisecond. I am down to swapping out POE, SR9 and cable next
unless anyone has things I can check. I have tried both with and without
nstream, turning off adaptive noise immunity, trying framer policy, lowering
the data rate to 6 meg only.

Ideas? Suggestions?