PHP problem with start simultaneous scripts

I'd like to use ajax to start asynchronously one php script. I try to use ano开发者_开发问答ther ajax request to get information about progress of it... but. I can't. Second request will wait for the first one. Is it cause by the nature of PHP? I guess that it can be also caused by handling session in both of scripts - Am I right?

//edit

Due to asks - I use opera web browser. I will check also firefox with firebug as you recommended to me.

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Once you have created an xhtml-request it can be that you need another one. For this usecase there are some libraries avalaible.