This sounds like the same issue that hit 48 today:
Where are you located, have you contacted other people on 48 in your area? Have you tried your sim in another phone?
It has been working fine for me in Dublin South.
What sort of problems?
If you haven't already done so then try rebooting the phone and manually selecting/connecting to the network again.
If that doesn't help then log a support request with 48 support.
Strange - everything working fine for me in D7/D1 right now. I can make/receive calls, send/receive texts and 2G/EDGE and 3G/HSDPA data works fine...