MultiSite, New user's blog gets error "?c=5"

I built a new windows server, installed IIS (version 6), MySQL (latest build as of yesterday), PHP using FastCGI (latest build as of yesterday), and also installed an ISAPI Rewrite module to replace the .htaccess with a web.config and allow proper URL rewriting.

Installed WordPress, created the database, set my pretty links, etc. Enabled MultiSite, went through that process successfully (using sub-directory mode). Everything appears to be working, can create sites, users, etc. Can view the sub-directory sites without any issues.

The problem arises when a user tries to log in to their site. When they are viewing their site (ex: webblog.com/user1) and click the “Log In” link, it takes them to webblog.com/wp-login.php instead of webblog.com/user1/wp-login.php. That might not be an issue, but whether you go to the first or the second URL listed above, the result is the same; after entering in the correct user1 information to log in, you get the error “You don’t have permission to view this site. Please contact the system administrator.”

I have adjusted the permissions on the wp-content folder to allow the iusr (internet guest account used with IIS) user read, write, modify permissions on the folder and all subfolders and files, but that did not help. I also saw a post on the web about changing the “wp_capabilities” entry in the table “wp_usermeta” to be:
a:1:{s:13:"administrator";b:1;}
instead of what was there:
a:1:{s:13:"administrator";s:1:"1";}
That didn’t help either.

I am including my web.access file as well as the code that WP wanted me to place into the .htaccess file. It is possible that I messed up my web.config file. Any help would be greatly appreciated. I should also note that my default “admin” user works perfectly; no issues with it.

web.config:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <rewrite>
            <rules>
                <rule name="WordPress Rule 1" stopProcessing="true">
                    <match url="^index\.php$" ignoreCase="false" />
                    <action type="None" />
                </rule>
                <rule name="WordPress Rule 2" stopProcessing="true">
                    <match url="^([_0-9a-zA-Z-]+/)?files/(.+)" ignoreCase="false" />
                    <action type="Rewrite" url="wp-includes/ms-files.php?file={R:2}" appendQueryString="false" />
                </rule>
                <rule name="WordPress Rule 3" stopProcessing="true">
                    <match url="^([_0-9a-zA-Z-]+/)?wp-admin$" ignoreCase="false" />
                    <action type="Redirect" url="{R:1}wp-admin/" redirectType="Permanent" />
                </rule>
                <rule name="WordPress Rule 4" stopProcessing="true">
                    <match url="^" ignoreCase="false" />
                    <conditions logicalGrouping="MatchAny">
                        <add input="{REQUEST_FILENAME}" matchType="IsFile" ignoreCase="false" />
                        <add input="{REQUEST_FILENAME}" matchType="IsDirectory" ignoreCase="false" />
                    </conditions>
                    <action type="None" />
                </rule>
                <rule name="WordPress Rule 5" stopProcessing="true">
                    <match url="^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*)" ignoreCase="false" />
                    <action type="Rewrite" url="{R:2}" />
                </rule>
                <rule name="WordPress Rule 6" stopProcessing="true">
                    <match url="^([_0-9a-zA-Z-]+/)?(.*\.php)$" ignoreCase="false" />
                    <action type="Rewrite" url="{R:2}" />
                </rule>
                <rule name="WordPress Rule 7" stopProcessing="true">
                    <match url="." ignoreCase="false" />
                    <action type="Rewrite" url="index.php" />
                </rule>
            </rules>
        </rewrite>
    </system.webServer>
</configuration>

What WP wants in the .htaccess file:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]