Remote Desktop Connection stopped working

I am running Windows 7 Home Premium.  I have a Remote Desktop Connection to my work computer (which is still in XP) which I have used successfully for years.  It has now stopped working, and giving me an error message of "Remote Desktop cannot find the computer ........."

I did a search for this problem, and found MANY others with the same problem.  Multiple fixes were offered -- some easy, some very complicated.  I performed all the suggestions that I felt comfortable with -- none worked. Among these -- I bypassed Windows Firewall; I bypassed my AVP (which is AVG).  I removed "printers" from the RDC connection.  I enabled Remote Desktop in "Services."    I was not comfortable trying anything that would change the registry, or anything that was just too complicated for my scant amount of computer knowledge.

I called Cox Support -- they "sent some changes to my router" and re-set it, but that did nothing.  They told me they didn't know how to fix it, and that I would have to resort to paid support.  My boss is reluctant to pay for such support because he is retiring, and I understand his position.

Our tekkie was able to connect to my work computer from his home, so I know the problem lies with my computer.  His hunch is that the problem lies with my ISP because he has seen this problem many times.

Having this Remote Desktop Connection fail is hugely inconvenient and extremely annoying for me.  Anyone have any ideas?