Would be awesome, if you can post your web.config here. I'm sure that you've wrong rewrites....
I took the web.config in the resource archive of the share.
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<rewrite>
<rules>
<rule name="rule 1N" stopProcessing="true">
<match url="^upload$" ignoreCase="true" />
<action type="Rewrite" url="/upload_photo.php" appendQueryString="true" />
</rule>
<rule name="rule 2N" stopProcessing="true">
<match url="^preview/([0-9]+)-([0-9]+).png" ignoreCase="true" />
<action type="Rewrite" url="/public/preview/{R:1}-{R:2}.png" />
</rule>
<rule name="rule 3N" stopProcessing="true">
<match url="^purchased/([0-9]+)-([0-9]+).png" ignoreCase="true" />
<action type="Rewrite" url="/fetch_photo.php?userId={R:1}&photoId={R:2}&tmb=0" />
</rule>
<rule name="rule 4N" stopProcessing="true">
<match url="^purchased/([0-9]+)-([0-9]+)_small.png" ignoreCase="true" />
<action type="Rewrite" url="/fetch_photo.php?userId={R:1}&photoId={R:2}&tmb=1" />
</rule>
<rule name="rule 5N" stopProcessing="true">
<match url="^crossdomain.xml$" ignoreCase="true" />
<action type="Rewrite" url="/crossdomain.xml" />
</rule>
<rule name="rule 6N">
<match url="^(.*)$" />
<action type="CustomResponse" statusCode="404" subStatusCode="404" statusReason="Not Found" />
</rule>
</rules>
</rewrite>
</system.webServer>
</configuration>