NFS 2.6.3smp-client <-> 2.4.20-24.9smp-server problem

Hi list,

I upgraded a RH9 box from 2.4.20-24.9smp to Vanilla kernel 2.6.3 (using smp as well). It look to be working fine except for the messages i´m receiving from dmesg command. After mounting a nfs server (wich is running 2.4.20-28.8smp , RH8 kernel) I started to get these messages on dmesg:

----cut here---
nfs: server 10.0.3.1 not responding, still trying
nfs: server 10.0.3.1 OK
nfs: server 10.0.3.1 not responding, still trying
nfs: server 10.0.3.1 OK

... and much much more like the above ... ---cut here---

Even with the messages I can do operations using the mountpoint from the client. I can save files, list directories and files, etc.

The question that arises after seeing these messages:

1) do the nfs code from 2.6 kernel is compatible with 2.4 kernel ?

2) what can I do to try to solve this problem?

I would appreciate any help.

-
Fabiano