MZ and Google

I'm using SeaMonkey with MZ 1.8.3.4e, and when I open up a new tab and go to 
Google, it reverts back to another tab with a different Google search and 
replaces that search. This only happens if I click on the Google bookmark 
saved on my personal toolbar. If I type in the Google.com URL, I can have 
multiple searches open. I deleted that bookmark and saved a fresh one, but 
it didn't help. I used to be able to have several Google searches open 
without typing the URL in. I don't have this problem when I use SeaMonkey 
without MZ. (I know this because I disabled MZ with the extension manager 
without thinking ahead and realizing that I couldn't easily add it back! And 
I did this once before too but obviously didn't learn from experience. 
However, the information about how to bring MZ back is online, so it's 
working now.) Thanks.