After receiving several ARP requests in succession the Ethernet stops working.
It looks like the Ethernet MAC no longer generates an interrupt when packets are received.
Anyone else have this issue?
I based my code off the ARM9_STR91X_IAR example from FreeRTOS 4.6.0.
I have since upgraded to lwIP 1.4.0.
It looks like ST has since updated their 91x_enet.c file to 2.0. The FreeRTOS example still uses v1.0, but I can’t tell if any of the 2.0 mods will fix this issue.

Try the code from http://developers.stf12.net/Ethernet-demo but these projects are old.

will do. thx.

I was unable to find the link to download the example you suggested, but I tried the FreeRTOSV7.2.0/ARM9_STR91X_IAR example and it has the same problem. The uip example does not exhibit this problem. 

Did some more testing. 
The problem does not occur with a 10Mb/s connection or with the uip example, only the lwIP FreeRTOS example.