System Information
Operating system and graphics card

Desktop Windows 7 64 bit, Nvidia Geforce 460gtx
Laptop Windows 7 64 bit Ati

Blender Version
Broken: (example: 2.69.7 4b206af, see splash screen)
Worked: (optional)

Broken in 2.70a

Short description of error

Bevel, edge weight, bevel sets back when touching Factor

Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps

I add a cube
I add a bevel modifier to it
I set the limit method to weight
I enter edit mode
I adjust weight by moving the mouse

Then i want to adjust the weight a bit more by changing the Factor settings in the lower left corner in the tool shelf. And in the moment i touch the slider the bevel sets back to no bevel.

One possible workaround is to set the Factor back to 1, and to adjust the bevel by the Mean Bevel Weight slider in the properties then, which is at zero.

What is highly irritating is that i have two sliders here for one action. They both do the same from what i can say. They adjust how strong the bevel has to be. One in the tool settings down left, and one in the properties. Add to that the bevel settings in the bevel modifier, and we are at three.

Attached a video in the zipfile to show what i do, a scene as a result of what i have done and a screenshot