I'm a network admin, and I see way more lightning damage to equipment travelling through the phone and network lines. The strike doesn't need to be on the wire, either. I've seen it several times where the strike was on a tree or building, and the pulse was powerful enough to get into the low voltage lines nearby and do some major damage.
In 2005, we had a strike on a pine tree near our building, and it did about $25,000 worth of damage to our network, phone system, computers and HVAC system. That was with the phone system being under maintenance contract. It would have been an easy $20,000 more if it hadn't.
Getting the USB adapter is a good idea. But don't be surprised if new problems start cropping up on that system. I would recommend that you back up anything important to you. It's a good idea whether you have problems or not.