When I run a preset that I made in LR3.6, the develop Basic panel reverts to the LR3 version. Clicking on "Reset" restores the LR4 version, but undoes what the preset was supposed to do, of course.
How can I make my LR3 presets work in LR4?
You'll need to edit the PV of the preset. If you had the PV 2010 as a sub-selection then your image got converted to PV 2010. Older presets don't automatically work in PV 2012 unless you edit them.
There are several settings that appear with new names, "2012" added, in the Develop Presets, I've discovered after comparing my old zeroing preset with a new one. "Clarity" is now "Clarity2012" and "Exposure" is now "Exposure2012". I guess that the only thing to do is to open each preset made with an earlier version of LR and change or delete the value names that do not exist in LR4. Of course, by the time I get all of that done, some clever programmer will have made a utility that does those things with the click of a button. It's unfortunate that Adobe chose to let us discover this ourselves and force us to edit, or at least check, every preset we have.
I hope that you're not suggesting that setting Clarity2012 to zero will give a different result than setting Clarity to zero. Certainly, setting Clarity2012 to a non-zero value may give a different result than setting Clarity to the same value in LR3. However, zero should be zero.
I was having the same problem and found this http://blogs.adobe.com/lightroomjournal/ (google is your friend)
You just run your LR3 preset, then change the process version to 2012, and it will try to recreate similar values in the new settings. Then just right click on your preset (or create a new one) and update preset with these settings. It is time consuming, but at least you only have to do it once.