EAP-TLS rekeying disconect issues

[Harry Lachanas]

We have successfully  installed  and enjoying ( really ) freeradius  
eap-tls setup for our secure wifi,  in an environment that looks like

Client-> Proxim-AP -> FW -> Internet -> FW -> Freeradius server 1.1.7

One issue that we observed was that after some idle time on the client, 
the client gets disconected and it fails to auto-re-authorize.
Then one has to disconect manually and reauthorize ... ( nothing in the 
logs of freeradius indicates that .. )

My questions are:

a) Is this a normal behavior ? ( I suspect not )
b) Is it a windows XP/driver etc  issue?
c) AP issue ( rekeying interval = 900  and no accounting profile enabled )
d) Firewall Issue ( ports 1812:1813 are wide open for access on the 
radius side  )  ?
e) Freeradius issue ??? ( The only attribute set in mysql radgroupcheck 
is GROUPNAME=prv-net , Attribute=Auth-Type,op=':=' , VALUE=EAP )

Any help/Hints  would be very much appreciated

Kind Regards,
Harry