The first thing to try is resetting the tools that are causing the problem. Do this from the drop-down menu in the Options bar (top left).
If that doesn't help, try resetting your preferences as described in the FAQ.
You either have to physically delete (or rename) the preference files or, if using the Alt, Ctrl, and Shift method, be sure that you get a confirmation dialog.
This resets all settings in Photoshop to factory defaults.
A complete uninstall/re-install will not affect the preferences and a corrupt file there may be causing the problem.
Did anything on the computer change prior to this misbehaviour?
All of the info John has provided is good. I'm a little surprised that he did not just say use the Pen Tool. This is usual response when anyone has trouble with lasso. I'm sorry to say that I have some sort of mental block to learning its proper use. I've tried many times but have no success. It's the one thing I need to have someone sit beside me, hold my hand and show me step by step.
To avoid the white screen problem try the following:
1. Do small selections at a time and keep adding to them. Do not run off screen. Make selection and copy to new layer. Make new selection and make another new layer and then combine them. Do so until your total selection is complete. You can then add a layer mask (if needed) and fine tune it for perfect selection.
2. Rather than scrolling to get your white screen to go away, try zooming out by using Ctrl and - (Minus) keys.
This is not a solution, just a work-a-round I've used for years. No doubt, others here may have better ideas, they usually do.
I have to truly Thank you and John for the very good information you
The first thing I did was reset the tool, that seemed to work but the tool
got hung up again, twice so I went ahead and deleted my preferences. That
also seemed to work
Then I remembered, from somewhere or some reading, that the alt and control
keys might be useful. I made a full selection (New) holding down the alt
key. When I tried to make a new layer doing the same thing it didn't work.
However I saved the outside selection. When I tried to add selections to
that it wasn't working (duh....I finally realized that I was supposed to
subtract them) but I saved them anyway. Then I pulled out some old notes
and refreshed myself on how to combine channels and did that...but it was
all black. It was good enough for me to begin my work and in the end turned
out to be the way I went for the project.
I re-read your email Q and subsequently did it your way and got a full copy
of the paperclip as it was scanned in.
I'm working with the channel...but am extremely happy to have the 'real' one
at hand if the need arises.
Again I want to thank you and John for helping me out of the deep pit of
frustration and helplessness Photoshop can sometimes throw one into,
especially under deadline.
For anyone reading this post I urge you to look at the link John included:
It's always good to revisit the useful things in the FAQ. I was very happy
working with CS2 and never had a problem with it...but had to change for the
new camera formats.
I thank you both again and will 'pass it on' if the opportunity ever arises.