Facebook load the canvas in the tab with some accounts

I'm experiencing a weird thing in an apps I'm developping.

The tab is loading the canvas. In the apps parameter I've filled the right path to both canvas and tabs.

Here is th开发者_如何学Goe apache log for the app admina account while loading the tab:

172.16.109.9 - - [01/Sep/2011:15:48:30 +0200] "GET / HTTP/1.1" 200 1593 "http://static.ak.facebook.com/platform/page_proxy.php?v=4" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/15.0.865.0 Safari/535.2"

I tried with another account, tester of the apps, he load the right file. Here is the apache log :

172.16.109.9 - - [01/Sep/2011:15:52:59 +0200] "POST /tab HTTP/1.1" 200 1314 "_https://s-static.ak.facebook.com/platform/page_proxy.php?v=4" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:6.0.1) Gecko/20100101 Firefox/6.0.1"

Is this a known Facebook glitch ?

Thanks everyone :)

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What do you mean by "loading the canvas"? Is the user redirected to your canvas version or the canvas content is shown inside the page tab, instead of the tab content?

There are some things that come into my mind, but I would like to know what is the problem exactly