hello, can you try to replicate the bookmarks behaviour when you launch firefox in safe mode once? if not, maybe an addon or hardware acceleration is interfering here...

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

if this doesn't solve the issue & you don't depend on the display of tooltips you can also switch them off - enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for the preference named browser.chrome.toolbar_tips. double-click it and change its value to false.

to the second part of your question: firefox 22 is now respecting the pixel density you've set on a system level in the windows control panel.

if you want to set the text size/pixel density in firefox different from that of your system's settings like it was handled in prior versions, enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for the preference named layout.css.devPixelsPerPx. double-click it and change its value to 1.0 (or any other zoom factor that fits your purpose; -1.0 is the default value and will adhere to the system settings).

WOW. about:config... 1.27 is about the way it was a few days ago, thanks.

On the bookmarks deal, no, safe mode didn't do it. Not a problem, just a stupid curiosity.

Thanks.

you're welcome :-)

Regarding the bookmarks, is the mistaken display a tooltip that appears when mousing on the Bookmarks Menu or Bookmarks Sidebar, or in the box at the bottom of the window in the Library dialog?

The tooltip (small box just below the cursor. The correct bookmark link shows at the bottom of the BM area and the correct site is selected. Very odd. See image.

This faulty tooltip issue does seem to be related to the new High DPI support in Firefox 22. See: https://support.mozilla.org/en-US/questions/957057#answer-457970