P: LR4 doesn't display point curve adjustments made in LR3

in the Lightroom Adobe Forum
http://forums.adobe.com/thread/971408
Michael Frye noticed that this way you can restore the tone curves for the "real" images but not for VIRTUAL ones. The following is an (unpractical) workaround for managing virtual images.
You can add a "buffer" image (a real one!) to both the LR3 and LR4 catalogs then, with both Lightroom opened:
1. in LR3, copy and past develop settings from the first virtual image to the buffer (real) one, then "write xmp data to file";
2. In LR4, "read metadata from file" for the real image, copy develop settings from it and paste them to the same virtual image.
Obviously you can use only one buffer image for all your virtual images but ... good luck if their number is more then 10... 😉

Please contact me too, thanks!

you may contact me to test the solution before distribution

I would appreciate that, too.
Glad to help on this one.

Yes, I would be happy to help.

yes please

Please note that the above workaround restores the original tone curves but the history steps remain wrong (without a real effect) and you loose the ability to go back in the develop process step by step. Obviously you can reset the setting and restart with the default ones.

yes please, contact me, thanks

I've probably found a sort of workaround!
I've made some "organized" tests and here I report my findings.
Using LR3.5, I prepared a "test catalog" using 4 images from 7 different cameras (28 images total): for each of them, I used both the original nef and the dng converted file (56 files in the catalog), all develop process was set to "2010".
The cameras were Nikon D70, D90, D200, D300s, D700, D5000, D7000.
I applied a strong tone curve to each image in a way that the appearance was heavily characterized.
Before exit LR3.5, I SAVED ALL THE METADATA TO THE FILES.
Opening and converting the catalog using LR4, doesn't show any visual change until I zoom in library or open the develop module: both these operation lead to a flat image with the strong tone curve lost.
Curiously, the history retains the original steps but they are ineffective: histogram and tone curve changes according to the visual change but for some camera the "new" tone curve is "medium contrast", for others (D5000, D90) is "linear", for D300s is "custom" (linear with blacks cut at 9.8%, and this explain my initial impression that D300s's curves were untouched, sorry). This last behavior may depend on the fact that I've different default develop settings depending on the camera serial number.
Finally, the update to the 2012 process only minimally changes the visual appearance and surely doesn't restore the lost tone curves.
And here is the UNEXPECTED WORKAROUND: doing a READ METADATA FROM FILES IT RESTORES THE TONE CURVES (and the 2010 process)! Upgrading the process to 2012 minimally changes the visual appearance again but now the strong tone curve is present and evident.

Sounds good. Just drop me an e-mail. I will be in at home this evening and I would be happy to test the hotfix and to help this problem to be fixed soon.

By the way, the old catalog v3 doesn't seem to be affected by the import procedure. Is that right? And I can overwrite a catalog with a backup catalog?