Descriptive Problem Summary:
semi-transparent pixels cannot be modified using the rectangular selection tool.

How I stumbled upon this
1)Open up a png file using dream maker (with semi-transparent pixels)
2)CNTRL + C to copy the png file.
3)CNTRL + V to paste the png file into an icon
4)Open up pasted icon state
5)Attempt to move/modify pixels using rectangular selection tool.

Easiest way to reproduce this bug
1)draw pixels with alpha less than max
2)attempt to select those pixels and move them using rectangular selection tool

Expected Results:
All pixels to be moveable with selection tool
Actual Results:
Only pixels that are completely opaque can be moved.

Workarounds:
No known workarounds