duplicate threads, how can I know how many I have?

[محروم.كوم]

Google notified me about duplicate pages I have,

I have a lot of threads ID's that are basically the same thread.

I've run the maintenance script that removes duplicate threads, but I'm afraid that it will delete threads that I need and that maybe duplicate but they aren't , (I have a lot of mess in my DB) - I stopped the script in the middle, it deleted 700~ threads, and there are a lot more I think.

how can I see the duplicate threads without deleting them? can I run a query or something?

another issue I have, when I enter forums that does not exists I get a blank page in FF and in IE I get 404 not found.
http://www.iatraf.co.il/forumdisplay.php?f=170

how do I fix it? __DEFINE_LIKE_SHARE__