Hmmm, I actually think I know what's going on here as I had pretty much this exact same problem myself today.
I had an E172 but unfortunately lost it. I received a replacement - the K3520 - in the post today. Plugged it in. Nothing. Fiddled about. Tried it a few times. uninstalled software, installed software. Still nothing. Was a bit miffed considering I'd waited in most of the day to receive a bit of kit that was now looking like a dud.
Then it occurred to me that the modem actually gets added as an additional network interface in the system network settings (System Preferences>Network) for your current location. There in front of me was the entry in the left column for the Vodafone E172. So I deleted it.
Bingo, it all started working.
So, I'm guessing that the network settings for your current Location include the E220 that used to work for you - and that this is causing a conflict. Therefore, I suggest either (a) create a new location for the K3520, or (b) delete the entry for the E220 if you're no longer using it.
At least, that's my guess. Hope that helps.
Now, I just need to get the damn thing working on Linux - my old E172 worked a dream