Do you have snap to grid turned on under the view menu?
Nope, it's turned off. Snap to point is turned on, but if managed to invoke this problem even on a blank document with only one object, so that shouldn't be a factor.
Normally when holding down shift and resizing with the scale tool it switches between resizing only the one axis (a smart guide line on the 90 degree axis) and resizing both axis' uniformly (a smart guide line on the 45 degree axis) depending on where my mouse is. When this problem manifests it only switches between resizing only the one axis (smart guide showing 90 degree axis) and some weird in-between state where the smart guide shows a +-30 degree axis line and states that it is a uniform resize and the info display shows only one axis resizing, yet BOTH are resizing, in a weird distorted proportion. It DOESN'T switch to a true uniform resize no matter where i move my mouse, and I have to release the resize, undo and do it again. I'm still not able to emulate this reliably so i can file a bug report....
I hope this isn't even MORE confusing...
I'm not seeing the behavior here...
There is a setting in preferences -> smart guides to specify the angles it snaps to, did you try changing that one? You might also try deleting your preferences since there is a correlation between the settings and your issue.