Procurve 2900 48G, 24 ports are inactive

[zz0]

Hello, I have a problem:
I have Procurve Switch 2900 48G and all my devices connected to first 24 ports work correctly.
But when I try to connect any device to one of ports 25-48 indicator on that device stays inactive and the device doesn't work.
All the lamps 25-48 on procurve switch are on.
Web-administration page for my switch shows disconnected ports 25-48, and port configuration page shows only ports 1-24 and A1-A4.
What can I do to use last 24 ports?

[zz0]

Problem solved, I just restarted it and 48 ports are ok

[zz0]

Problem appeared again.
I restarted it yesterday, it worked, but now 25-48 lamps are on, but ports are inactive.
Whats it?
Is it defect and do I need to send my switch to service?

[Jack Howes]

I had the very same problem with my 2900 48G switch. After updating firmware and sending the Tech-support output to the Procurve network team, they sent me a new switch. The error has not appeared on the replacement switch. I'm guessing it was some type of HW problem.