Express 500 switch

[telering]

Dear all,

we cascaded two cisco catalyst switches using 10/100/ports,
& one 500 - is cascaded to 3560 corporate LAN, & only IP phones are conneted to express 500 switch

every time express 500 gets alret on the switch & gets hang, all IP stop working, only after reseting the switch everything is normal.

when we see the erors it says switch opretaion is normal.

any work around .
any thoughts highly appriciated

Regards