Problems Caused by User Agent String Too Long
I recently had something happen to my machine that has caused me all sorts of havoc. There are many symptoms of the same problem. This all seems to have begun after a Windows security update (KB958687) was installed on my machine. Interestingly, even after uninstalling that update, I still have the problem. I haven't fully researched why that update caused this to happen, so maybe the update isn't exactly the culprit, but at this time, I believe it is.
Part of what made this so difficult to resolve is that there are so many symptoms of the problem. With so many symptoms, there are many vectors to research that are so vague, it is difficult to isolate the actual problem.
I will begin with the symptoms I had in the order that may make it most easy to identify.
1. The About box in Internet Explorer (IE, IE6, IE7) causes an error message dialog box to appear stating:
An error occured in this dialog.
Error: 53
Not enough storage is available to complete this operation.
Please forgive the formatting. I am trying to make this as search engine friendly as possible. Here is an image of the IE About box error message:
2. I had improperly rendered menus on some of my web sites.
Improperly rendered menus in Internet Explorer (IE)
Here is an image of the menus of this site (netsplore.com - http://www.netsplore.com) as improperly rendered with the problem. If your menus of this site look like the following, you may have this same problem.
Notice the area circled in red. That area should not be there. The menu text is extending beyond the space it is supposed to be in. Also notice the blue line above each menu text. Instead, they should look like this:
3. I had wrong z-ordering of html elements. In particular, I had a dropdown list (html select control) rendering on top of a menu when instead, the menu should be on top of the dropdown list.
Improper z-order of html elements
Here is an image of the elements with the wrong z-order:
Here is how it should have looked:
4. I could no longer use the financial software I had been using because the appropriate version of flash could not be detected when installed. It would instruct me to install Adobe Flash Player version 9.0.124.0 or higher. If I clicked on the link to install it, it would install, but then still tell me I needed to install Adobe Flash Player version 9.0.124.0 or higher.
Adobe Flash Player version 9.0.124.0 or higher was not detected when installed
Here is an image:
All of these problems are all apparently caused by the same problem, that is the inability of IE to properly determine the user agent version due to a limit in the length that it can be. To resolve this, I had to eliminate a registry setting to make the user agent string short enough. Here is some javascript that illustrates the problem:
<script>
document.write(navigator.userAgent.toLowerCase())
</script>
Put that in an html file and load the file into IE. When I do it with the problem still in effect, I get this:
mozilla/4.0 (compatible; msie 6.0)
I think this is because the string gets too long, something goes wrong, and this must be the default. This apparently causes things to get rendered wrong and havoc to happen.
To resolve these problems. Look in the registry at:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent\Post Platform
When I do, here is what I see:
Having all those entries on the right side apparently makes the user agent string too long. I don't know yet (check this blog for a follow-up post) which one is the best to remove, but for now, I will remove the bottom one (MS-RTC LM 8) to resolve the problem. I will have to launch a new IE process for this to take affect. Make sure you do indeed get a new process running so that it re-reads the registry. If you don't know how to be sure of this, check your process list (press CTRL-ALT-DEL keys, press "Task List ..." button, select "Processes" tab) and make sure there are no instances of iexplore.exe running, then launch IE again. Then, you will hopefully find that all the problems are gone. Maybe you will need to remove more than one of those entries. I don't know yet how important any of them are.
Interestingly, once I remove that last entry, if I rerun the above javascript (in a new IE process of course), I now get this:
mozilla/4.0 (compatible; msie 6.0; windows nt 5.1; sv1; hpc factor; gtb5; mozilla/4.0 (compatible; msie 6.0; windows nt 5.1; sv1) ; .net clr 2.0.50727; .net clr 1.1.4322; .net clr 3.0.04506.30; .net clr 3.0.04506.648; .net clr 3.5.21022; infopath.2)
Now all my problems are gone. The IE About dialog box displays properly. I don't get stuck in an infinite loop trying to get the correct version of Adobe Flash Player installed. My html element z-ordering is correct, and my menus render properly. This took me quite a while to troubleshoot and resolve. I hope it helps someone.