At work we've got a problem with our wireless network.

We've got a lan, which consist of two subnets.
In one subnet, the devices with static IP-addressen are gathered, such
as printers, access points, etcetera.

The other subnet is for the clients.
A single subnet is not enough to hold all the devices and clients.

The gateway consists of two routers in HSRP, which both have an
IP-address in both subnets. An HSRP IP-address is also for each subnet.

Regularly, a wireless client loses the IP-connectivity, or so it seems.
Wireless link is good, IP-address is present, but communication with
anything other than the local lan is not possible.

Client can ping to other stations on the same subnet, to the secondary
router, but not to the primary router or HSRP IP-address.

Pinging from primairy router to client is also not possible.

Can anybody provide me with a clue as to what may cause this problem?