ColdFire Ethernet with LWIP and FreeRTOS

I’ve ported the demo LWIP_MCF5235_GCC to the MCF5282 with CodeWarrior as the C compiler.  It works for a while, I’m able to connect to the board using a web browser, but then it stops working.  I can’t stay connected for more than 1 or 2 minutes.  I noticed that once it crashed, the task are still running (I removed the vErrorChecks task) which is good, but the ISR (triggered by incoming frame) isn’t triggered anymore.  I boosted rx task priority level, Boosted ISR level and priority, looked for wrong data in the Ethernet Controller registers. Any clues on what could cause the ISR to stop working? Thank you Francois