Why do I loose lens perspective adjustments made in Lightroom when I open the image in CS5

Question

Question as title above

Answer 1

Probably because you are opening the image into CS5 via a version of Adobe Camera Raw which does not provide the same support or use all the same parameters and settings, as your Lightroom does. For example, if you have used Upright, that is something that only the later ACR versions understand, and in order to use those versions, you would need a newer version of Photoshop.
In such cases, you are better off having LR render the conversion and LR settings into a file (TIFF or PSD) that is already saved to disk in that format, before PS sees it.
That way, PS has no need to involve your ACR at all, or to lay itself open to potential incompatibilities there. It only has to understand the completely standard pixel data inside the PSD / TIFF.
You will at some point have been given a LR warning dialog about ACR version incompatibility, offering the choices "Render in LR" / "Open anyway". If you have clicked "always do this" after selecting "open anyway", you will no longer be getting this warning. You can re-instate it using LR Settings / "Reset all Warning Dialogs". Then by giving the response "Render in LR" instead, you will get a full and complete implementation of all of your LR adjustments, into Photoshop, from the standard Edit in PS feature.
That arrives in PS as an already-saved and already-named file; you just need to Save (not Save As) when you are finished there.
Another approach, is to set up an additional named external editing "preset" in the LR Settings / External Editing tab, referring to your Photoshop program file, with your choice of file type, bit depth, colourspace (which can vary from the ones configured for your main "Edit in PS" option). This name becomes a new entry in the "Edit In..." menu. Using that always carries out a "Render in LR" procedure, regardless of the state of the general warning dialog mentioned above.
regards, RP