LR3.x is compatible with ACR 6.x that comes with PS-CS5 and whatever versions of Elements that were released when some version of ACR 6.x was the current version.
LR4.x is compatible with ACR 7.x that will come with PS-CS6 and should be compatible with PSE10 with at least an ACR 6.7 update which is not quite available, yet, but more compatible with an ACR 7.1 update that I would expect will come out not too long after PS-CS6 ships.
I think that’s why LR3 was happy with ACR 6.2 while LR4 is not.
If you installed Photoshop CS 3, the last version of ACR that is compatible with that version of Photoshop is version 4.6. If you are going to use that version of Photoshop then it will be necessary for you to render a copy with Lightroom adjustments and send that to Photoshop. CS 3 is now in nearly three versions old, and is no longer supported and no updates for anything related to CS 3 will ever be available.