This post is about an interesting issue that I recently worked where firewall administrator published an internal web site through ISA Server 2006 and when it tries to load the main page some components didn’t load correctly and the error message below appeared:
The issue didn’t happen when browsing the web server directly (on the internal network) and the browser was able to load the whole page.
When we have client side error like this and we are using SSL, it is always a good idea to use HTTP Watch to read the content and see where is failing. It also important to get a working trace and a non working trace so you can compare both results. On the working HTTP Watch trace we see that some DLLs were being called by the application:
Since I couldn’t see this call on the non working trace I decided to try to access the DLL using the external URL (for example: https://www.contoso.com/app/myapp.dll) and it found the file but failed to download.
Different symptom but same root cause
With all these elements I could conclude that the issue was exactly the same one that I that I wrote on post Unable to Download an Office file from a Web Server Published through ISA Server 2006 Here it is the explanation why it was failing:
Notice the highlighted which emphasize the reason why it can also fail for other files other than office files. The article mentioned above explains how to fix the issue.