Today while I was working in Illustrator I noticed something particularly annoying. For some reason when I moved a guide flush with an anchor point or tried moving any object flush with a guide, the object or guide would jump away from where I placed it by a pixel or so.
I initially thought maybe my smart guide or snapping settings were turned off, after checking everything I could think of I came to no resolution. I was almost driven mad, I have been doing this daily for the last 10 years, why suddenly couldn't I do this.
Turns out the Fix was a setting I have never heard of before. In the Transform dialog box there is a tick box called "Align to pixel grid." unticked it and problem solved. You will notice that this setting will relate to a selected object, so you will have to select something (or everything) in order to turn it off for that object.
Hope this helps someone as it really is an annoying feature not to know about.