RPC is not "called" by a dial up networking connection. By default, dial up does not allow connection to system ports (132 - 139). It requires special configuration to allow these ports to be accessed through dialup, like assigning PPP to the dialup adapter.
It really all depends on how your networking is set up. When you use DSL or cable, your computer is basically seeing that connection as a local network connection. Dialup uses a sort of translation software which tricks the PC into seeing it as a local connection. If you have a VPN (Virtual Private Network) adapter, such as installed by AOL or to access a corporate network through dialup, it might still affect you. The adapter I refer to is a software setting, not hardware.
Here's what I posted on another board about this whole situation. I hope it can be of help to someone here too:
"Let this serve as a (painful) reminder. Visit windows update at least once a week. If you run XP, you can even set it to do so automatically.... even completely unattended! Also make sure to keep your antivirus definitions up to date. And if you don't have a router, at least run a software firewall. Preferably use a router with NAT and a software firewall.
For anyone who gets hit with this. Here's a free removal tool from Symantec:
http://securityresponse.symantec.com/avcenter/venc/data/w32.blaster.worm.removal.tool.html
It works. I've been referring friends to it all day long. Why they wouldn't listen to me about taking precautions in the first place is ..... bleh!
Once you run that and get rid of the thing, go to windows update:
http://windowsupdate.microsoft.com/
And download/install anything listed as a critical update.
Your system will thank you, and so will the rest of the internet. As with many virii, this one turns your machine into a node which will try to infect others. This one also generates a LOT of net traffic, slowing everything down for everyone."