asp scriptmanager vs ajax toolkitscriptmanager

Question

I am working on ajax based web application. I am getting typical "Javascript out of memory exception" on modelpopup dialog when ever I used asp ScriptManager on my home.master page

But it is working perfect with ajax toolkit ScriptManager.

Is there any difference b/w ASP ScriptManager vs Ajaxtoolkit ScriptManager.

Another note is - This issue is happening only on my computer, it is working perfect in other development machine.

Thanks for you help!!!!!!