HTTP 403.9 - Access Forbidden: Too many users are connected

Ah... bastards!  That's what I figured, but I wasn't able to find anything to tell me for sure and didn't really have the time to spend doing too much looking.  Thanks.

No problem. I guess you will have to pay for a server OS :)
Thats MS for you

Actually, a limit of ten simultaneous connections is quite generous: since each connection only lasts a split second, you should be able to serve up hundreds of files a minute with that setting.

So the reason that you get this error is probably that you allow each connection to stay alive longer than that. To turn this off (and get your web server performing much better), just do the following (in WinXP):

1. Right click on My Computer, click Manage

2. In the Computer Management Console, go under Computer Management > Services and Applications > Internet Information Service > Web Sites

3. Right click on your web site, click Properties

4. On the Web Site tab, uncheck "HTTP Keep-Alives Enabled"

Now unless you get a million hits a day, I'll bet you never see that error again. So the real problem is that this fix isn't documented anywhere, and the error message doesn't help. Enjoy!

Quite generous??!!
Can't even serve up one web page if that page has dependencies on web services running on the same server. For example. You request a page, it is served. Yay! How generous to be allowed to send a file across the wire. Now you enter login information and hit submit. The real fun starts. First, the new login verification page gets the security token for you from the Login Web Service, then sends this token to the Utilities service to determine if this user has any administrative right. The utility service then queries the resource permissions service, then for each entry queries the resource instance service, then the resource service, and finally the resource type service since this is where the determination of whether a particular resource instance is a administrative resource or not. OF course it never gets that far because the magic number of 10 connections are made (not really, but there is lag between when the connection returns from a call and when the connection handle is released by IIS), and your wonderful work for the last month returns back to 403 Access Denied. So you pull out some hairs tryin to make sure all the permissions and such are kewl. Not that I am bitter ;) But with Web Services bein pushed down developers throats, one would think that the forcers would take into account the possibility of multiple dependent web services exceeding the max on a developer workstation. Of course it all comes down to licensing, as any developmental headache with MS does. But I wouldn't say that 10 is any where near sufficient. Maybe 100. At least I could get one page to load. Heaven help me if I throw some images that download asynchronously on the page. I will prolly have to upgrade to the next $2000 web platform of a product that I can download for free under a different name (apache???)

ha ha ha
Dunno what people want out of free services ... I mean come on guys you are getting a free unlimited (limited only by your hard disk size) webspace. Once the "HTTP Keep-Alives Enabled" is unchecked the problem gets more or less solved and it even reduces the burden on the connection ...... so chill out and be happy with what you have. :)

Btw the solution given by "nbfriend" is more acceptable than the one which is labelled as "Accepted answer" .... Are the solutions termed by first-come-first-served or by their usefulness? I'm new here so was just wondering :S

yeah, also if you have antivirus software with script blocking running you will get this error

  I have this same problems and NOTHING WORKS except rebooting the machine that the IIS is running on!

I find I can fill the 10 connections in 1 click.

We are in the process of building a web application that uses iframes, lots of them. It had to be done this way unfortunetly, since we have many calls happening at the same time, 1 simple click may change 10 things, then add the fileupload factor, the fact that alot of the graphics are done in aspx, 10 connections are used in 1 click :(