Hi John
After the grid is rotated. Select angled guide line, you can leave all the snaps you normally have on. Have grid snap on. Then press w to set a working point, click to set point you want to use as reference for your guideline. Then type r to open 2d coord box , ensure its set to relative grid xy , and enter you offset positive or negative and it should work.
Make sure that there are no locks set like normal,ortho etc.
The picture you embedded did not show up, I am not sure why. The file I attached I drew 2 guidelines 1" in +x and -x using the steps above. I also embedded a pic to see if it works.
Regards
Jason
Regards
Jason