Could you please tell us the version NUMBER of Lightroom that you are using?
Also please state the operating system version number.
What CPU do you have?
Please be specific, what actions in Lightroom are slow?
Are you doing lots of brushing or spot healing on a photo?
What size (in pixels) is your monitor? What size in pixels are your photos?
I use Lr6, my computer runs with Windows7, CPU is Intel Core i5 2500K, monitor 1920x1080p. Photos around 6000x4000p.
Any action in Lr are slow (very very slow) even to display a photo (10 seconds). I use a lot of brush but I don't think I am abusing...
I had install a Wacom Intuos M few weeks ago but I uninstall it to see if the Lighroom performence is beter... nop !
Lots of brushing will cause these slowdowns. Your CPU is somewhat old and slow as well by today's standards. I am not surprised you are having these problems, especially since photos have gotten larger over the years, and yours are now 24 megapixels.
As an experiment, you might want to try creating a new catalog, take 10 or 12 pictures that have no real value, they will only be used for the experiment, import these 10 or 12 into the new catalog, and then do all of your editing, but don't do any brushing. Is Lightroom faster?
I tried what you suggested and your right, Lr6 is much faster. Perhaps over the month, I was doing more and more brushing and didn't even noticed it...
Regarding the error message ("adobe media core.0 has stopped working") that appeared when I used to quit Lr6, I saw in the message's details something about Quicktime. So I have reinstalled Quicktime and the error message has now desapeared.
Thank you so much for your help.