I like to use both LR2 and Bridge 2 (PS CS3/Bridge) and all edit that I make in straight ACR 4.5 do not show in LR2 but the ones I make in LR2 do show in Bridge and when I open that image in ACR.
What setting do I need to change in either ACR or LR2 to make the edits done in ACR show up in LR2.
In ACR you have an option to save the adjustments to sidecar files (default) or a centralized database. At least it used to be so. Make sure the adjustments are saved to sidecar files.
Also, in LR you have to read metadata from files - the adjustments won't load automatically from those .xmp sidecar files.