asterisk users - Jun 2007 - Issue with Grandstream ATA 496.

Hi everybody,
I have bought one 496 to use as ATA for two analog extensions in my office.
I'm experiencing strange behaviuors. The ATA blocks itself and needs to be
rebooted. Sometimes it hungs the lines(ISDN bristuffed HFC single isdn
line). It was update to last available firmware.
Has anybody those issues?

Best regards

Mauro