I compiled LyX 1.3.1 with xforms 1.0 and enabled instant preview. I went to the middle of a document with equations, put the mouse somewhere in the text, and dragged a bit upwards to select a part of the text. Instead of selecting just a small portion of the text, the display was rolled down quickly and I got a big portion of the text selected. It seems that this automatic scrolling when dragging the mouse to select is too quick and not as reliable as without the instant preview.
Then, while a part of the text was still selected, I went to the Preferences and switched off the instant preview. Then I saw the following message appear on the console: In badwin_handler [events.c 535] X error happened when expecting only BadWindow/Drawable But no adverse effects were visible in the LyX window. I was not able to reproduce this immediately afterwards. -- Serge