Resizing in Illustrator CC using the Bounding Box is no longer accurate. What happened?

Question

In Illustrator CC, resizing an object using the bounding box is no longer accurate. Snapping to other objects or the grid or anything is completely wrong and, worse, inconsistent. Here is a single box being resized 3 times to the same object. Each time, it becomes a different size.
I used the center-left handle to resize the black box, snapping it to the right edge of the red box. You can see that, each time, it "snaps" to the edge incorrectly. My 80 pt box becomes 78.479 pt, then 79.295 pt, then 79.518 pt.
This is totally unacceptable, obviously. I'm not sure what the point of guides are if they aren't actually guiding. Does anyone have a fix for this?

Answer 1

Ethan,
Did you reinstall after updating to Yosemite? I believe the right order/way is to update the OS first, then reinstall the applications, see 6) below.
Or you may have a look at the list since something is obviously wrong.
The following is a general list of things you may try when the issue is not in a specific file (you may have tried/done some of them already); 1) and 2) are the easy ones for temporary strangenesses, and 3) and 4) are specifically aimed at possibly corrupt preferences); 5) is a list in itself, and 6) is the last resort.
1) Close down Illy and open again;
2) Restart the computer (you may do that up to 3 times);
3) Close down Illy and press Ctrl+Alt+Shift/Cmd+Option+Shift during startup (easy but irreversible);
4) Move the folder (follow the link with that name) with Illy closed (more tedious but also more thorough and reversible);
5) Look through and try out the relevant among the Other options (follow the link with that name, Item 7) is a list of usual suspects among other applications that may disturb and confuse Illy, Item 15) applies to CC, CS6, and maybe CS5);
Even more seriously, you may:
6) Uninstall, run the Cleaner Tool (if you have CS3/CS4/CS5/CS6/CC), and reinstall.
http://www.adobe.com/support/contact/cscleanertool.html