Problems with layers being turned off in viewports

[jhartley]

I'm having problems with layers turning off in viewports and I'm not doing it. I will be working on a ceiling plan in a viewport on a tab and then switch to the floor plan tab (which is in the same .dwg) and some of the layers have been turned off. I go to the layer manager and turn all of the layers back on and the correct layers show up (the viewport freeze/thaw settings are retained). Then I go back to the tab with the ceiling plan, do some work and then switch back to the tab for the floor plan and some of the layers are turned off again.

Is there a system variable to correct this issue?

Any help is greatly appreciated. 

[rkmcswain]

Since layer visibility cannot be control per viewport using ON/OFF, then this is a global OFF being applied to the layer(s).

Restoring views can change layer states.
Restoring layer states can do the same obviously.
What else might be happening (besides normal commands like LINE, ERASE, MTEXT, etc) that could be affecting the layer state?

[jhartley]

The only thing I'm doing to the layer states is isolating a couple of layers in a viewport, making the changes and then unisolating them. This is when the problem begins - certain layers are turned off when they should be on.

[jhartley · Accepted solution]

I figured out what happened. In the Layer Settings dialog box, under Isolate Layer Settings, the option to turn off layers or freeze them in a viewport was changed to Off. After changing the setting back to VP Freeze, the problem went away. Attached is a screen shot of the dialog box.