Construction Line Conundrum

[ColinPearson]

Hey All:
I have this problem with construction lines - maybe it's a misunderstanding of how they're supposed to work on my part. (And I know they're kind of old school and I should use some direct input probably for some things, but I like 'em )

If I click out in blank space, they seem to always act fine - that is, they'll rotate to any degree based on a next point or go ortho if that's turned on.

But, if I click first on a snap (any type, mid, end, etc), then move my mouse somewhere else to pick a second point, SOMETIMES the xline slides along along with my cursor, staying aligned to one of the two ortho directions. It does NOT stay fixed at the first point picked and additionally, will not go to any other angle (regardless of where the second point is). Sometimes it works okay when I start from a snap.

Ortho, Polar, etc all have no effect on this behavior.

Anyone??? Thanks in advance, I'm getting a little crazy at this point.
AutoCAD Mechanical 2010
XP

[Croweyes1121]

Tell me you figured out what was doing this! I'm going nuts, too! Same issue! HELP!

[rkent]

It sounds like you might be in DYN mode and picking on something with a z value on one end, or maybe your UCS is not set to world.

[Dadgad]

Welcome to the forum.
I suggest you check your OSNAPZ variable, as shown in the image.
Setting it to 1 should fix that.

Should that not take care of it, per rkent's previous good hypothesis, then set your OSOPTIONS to 3, like in the second image.