ASP.Net页面有时在页面加载前冻结

I have a pretty standard ASP.Net page written in C#. Most of the time it loads just fine and works a treat but occasionally the page won't load, I've inserted break points in the Page_PreInit (I don't actually have any code here, I've just created the function so I can see if the codes getting this far) but it's not getting this far. Any ideas where I should start in looking for a solution?I have a pretty standard ASP.Net page written i