As mentioned before, I had, thoroughly tested the 3.5 nightlies, but never found it necessary to install 3.5, as I, always, do with programs in development. 3.5 looked good, and, perhaps, faster, but gave credit to the fact that there were few compatible add-ons .
3.0.11 was, still, my default browser.
I installed 3.5 in a separate folder, using the same profile, previously, used for the nightlies.
I believe that there was box which selected 3.5 as default, on installation, so I unchecked the box. I noticed a marked slow down with 3.5, but did not try 3.0.11 until a few minutes ago, when I was trying to get some bookmarks which were found only in 3.0.11, into 3.5.
To my surprise, the 3.0.11 shortcut led me to check some add-ons, a sign that I was not working with the customary path. I checked the 3.0.11 path from Properties, and found that it had the 3.5 path. To give an example, 3.0.11 used the default path in Program Files, while 3.5 used an abandoned folder. The Firefox 3.0.11 had the same path as 3.5. It was nuisance, as I had to enter, manually, the proper Target plus profilename, and start in. Only after doing that 3.0.11 opened as it had before.
As 3.5 goes, I don't know the reason of its sluggish behavior. I will have to flip flop the two versions, and see if there is any explanation (paranoia on part of 3.5?).



