PSE8 for Mac odd problems

Question

When I first got it, it seemed to work as expected until very recently. Yesterday, I tried it first with, and then without a Wacom Intous 2 tablet, and it refused to draw a line with brush or pencil tool except for vertical or horizontal, as if I was holding the shift key, which I wasn't.
Other peculiarities that have appeared at the same time:
Brush cursor keeps showing as eyedropper cursor, and sometimes even picks up a colour like the eyedropper should, without eyedropper being activated.
Rectangle and ellipse selection tools show up as perfect squares or circles until released, then adopt the correct shape based on the start and finish dragging.
Not tried much else as not being able to draw freehand is a showstopper anyway.
The last drawing I completed with it was a diagram which  consisted entirely of vertical and horizontal lines, plus text, and without the  graphics tablet, so not sure if it was happening then. Anyway, the tablet has worked quite happily with PSE8 when I had last tried it, and I have just  tried it with OpenOffice drawing and seems normal, so I think  the problems appearing to start with the tablet was a coincidence.
Googling for PSE and straight lines just shows me how to get them, so not much help.
I have tried forcing it to genereate new preference files by the cmd-option-shift when launching PSE, but it still happens.
I have not registered it with Adobe.
Is there something I am missing?
Should I uninstall it and reinstall PSE8?
If so, can I just drag it to the trash, or is there some other tidying up to do?
If I do that, should I deactivate it first bearing in mind it will go back on the same machine?
Can I only deactivate it a limited number of times, if something similar happens again?

Answer 1

Thanks. I uninstalled using the Uninstaller. It was going to go back onto the same hard drive, so I did not deactivate, not knowing how many times I am allowed to do that.
Trying a reinstallation, but the first attempt said it was incomplete.
Followed the instructions for another attempt, and it still says it is incomplete, listing :
Photoshop Camera Raw
Error:
Error 2.
The Get Support button took me to Get Support Advisor, but going to the United KIngdom page replaced that with something else that looked like an advertisement.
Downloaded Adobe AIR Mentioned on the Get Support Advisor page, but no idea what it is for or whether I need it.
Instead of messing about further, I have just tried to run what the PSE8 software that has gone in.
A quick check seems to show it working again, freehand lines and no unexpected eyedropper, and selection rectangles look right.
Tablet seems to work OK too.
It is getting late here so I will have a more thorough check tomorrow.
Thank you for your help.
Nick