Desired pop-ups disappearing since upgrading

Awhile back, I upgraded to Mozilla v1.7.8 from an earlier v1.7.x 
release. I know the latest now is v1.7.11, and I will upgrade soon, but 
I'd like to solve this problem first.

Since upgrading, pop-ups that I want to see, on sites such as 
Pricegrabber, open briefly but then close before I can read their 
content. They are only open for a fraction of a second. I can view them 
by finding the link in the history file and opening a new tab, but this 
is a nuisance. I don't see anything set wrong in my preferences. Any 
suggestions? Thanks!

John
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