Oh no! Not another "line" command question!

[bleeargh]

I have an architect client who is running AutoCAD 2005 on his machine. He showed me a residential floor plan that he was doing and a strange phenomena was happening with his line command.
Here's the sequence

1. Has an existing horizontal line that is 12 units long (you can put in whatever units you want depending on what continent you live on)
2. Wants to draw a new line off of the right endpoint of the existing line.
3. Intiates line command
4. Grabs right side endpoint of existing horizontal line when prompted for "specify first point" (osnaps are already set, ortho is on)
5. He pulls the mouse away from the existing line and types a random number, lets say 4, and hits return. Naturally, a new line is then drawn 4 units away from the existing line.
6. Okay, here's the weird part. In the exact same sequence he grabs the right endpoint of the existing horizontal line and pulls his mouse back OVER the existing line so that the new line is over the top of the existing line. He type in 4, hits return, and autocad doesn't draw the line.

In other words, when inputing off from the keyboard over an existing line the line command doesn't take. If he goes in any direction away from the existing line it works. Why is this?

[CADTutor]

Does this still happen if you turn off your running osnaps?

[bleeargh]

I just called him and had him run the exercise. He said it works when he turns his osnap off. That is odd, though. I have never encountered that problem and I have my osnaps on all the time.

[Spageddie]

Get him to check that Priority for Coordinate Data Entry is set to Keyboard entry except scripts
This can be found the USer Preference tab of the autocad options dialog

[bleeargh]

Thank you Spageddie! That did it.