> When it's hyper-sensitive, moving the cursor on the desktop opens a translucent rectangle; where this overlaps an icon, the icon becomes selected. The cursor tip sticks to a corner of the rectangle; the diagonally opposite corner stays put when I move the cursor. Lifting my finger tip eliminates the rectangle.

That, in particular, and other of your symptoms sound like your your (whaddayacallit) click-bar (?) is badly out of whack and quite possibly in need of replacement. (The issue I quoted is precisely what happens when you move your cursor in a Finder window while clicking.)

(Edit: Sorry... I hit the wrong radio button and posted prematurely.)

Quote:
I update some software, but I haven't updated applications I don't use or installed updates which relate to features I don't use, according to the remarks in the lower pane in the Software Update window. What do you think of this as a general rule? Could I have let myself in for a problem this way? (Still running OS X 10.5.8 with recent updates.)

Tough question to answer sans details, so why don't you post a list of your "Ignored Updates?"

Last edited by artie505; 08/15/10 10:14 PM.
The new Great Equalizer is the SEND button.

In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire