I have seen this bug many times before, but never could pin this down with a save file and exact sequence of moves and all.

Well here is one example (http://www.civfanatics.net/uploads5/BuggyVikings,_1610_AD.SAV).

Open up the save file. You should have focus on an artillery piece in the town called LilHammer (yes its a viking town).

Just right click and say fortify all and sit back and enjoy. :( Your cpu will go to 100%, and you computer will freeze and eventually after 10 minutes or so the game will crash.

The game will not crash of there are no automated workers.

Version - PTW 1.27f
System - Pentium (dual CPU) Windows XP SP1.

Anyone else seen this? Is there a fix?

The way you describe it doesn't make me eager to download and try it ;)

A good reason not to automate workers. I will take a look.

YES!!

It happened to me. Actually the reason I registered here...
My worker was on automat clean up pollution and was moving from one end to the other end of the map just to clean up.

While in English territory, with RoP, it encountered some fortified units which were hidden under fog.
The worker kept going up and down, probaply looking for a rail to continue on, but since Elisabeth had placed her damn guerillas on her rails he couldn't see them when up, therefore going down to encounter another guerilla and so forth.

And this was on a game I had played on for 4 straight hours, without saving! And I was winning big time.

Never Automate your worker must be the lesson...

Did you have an autosave? If so you can use it to recover the game save.