This morning I patched using version 1.34. Started the game fine but when I go to load a saved game I get error msg and cannot load it.

Thankfully, before installing patch I made a new folder called patch this version of fallout1 and copied all of my fallout1 folder into it and patched it. So I closed that fallout and restarted old one and no problems.

Most patches make old saves redundant. This is to do with certain files being overriden. If patches don't physically overwrite other files, it can be as easy as removing the patch files to revert back to an original state.