Windows XP - having trouble printing to shared printer on my desktop from my notebook computer on wireless network

I am running Windows XP Professional on both my desktop computer and my notebook.  These are in my home, where I have a wireless network setup.  I have shared out my desktop printer, and have setup the notebook to print to that printer previously.  I initially used the netbios machine name to find the printer during setup, which worked fine the first time I did the setup.  After a week or so (I don't print very often, by the way), I tried printing again, but my notebook could not find the printer (even though my desktop machine was on and able to print to the printer itself).  I then tried removing the previous printer install from the notebook and tried adding it in again, this time using the ip address (i have static addresses assigned to each device on my home network).  It worked -- but again, just like before, it only worked for awhile, and eventually could not "locate" the printer on the network in future attempts to print to it.  I now again have tried removing the printer install from before (from the notebook), but can not even add it in this time at all -- it doesn't find the name and it also can't find it by ip either!

any suggestions on how to correct this problem would be great.  I just don't get what's happening with it.
thank you.