An error occurred on the server when processing the URL. Please contact the system administrator

Ok, have a client. Site is running fine. I went to develop locally on a new laptop running IIS 6. Browsed through the site locally, then hit the following message:An error occurred on the server when processing the URL. Please contact the system administrator.
I couldn't figure it out, and why did I see this generic message. To resolve it took some time, but here's what I found:
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-Open up IIS 6
-Choose your site. I have multiple sites set up on different ports
-Look at the "IIS Home" for this site.
-Double click on the ASP icon
-Expand "Debugging Properties"
-Change "Send errors to browser" = true
-Reload your page.

Here's the new error:
Active Server Pages error 'ASP 0131'

Disallowed Parent Path

/xyz/zzz.asp, line 4

The Include file '../1243.asp' cannot contain '..' to indicate the parent directory.

I tried to make a quick fix with some other options, but it didn't work. Again, it's another setting in IIS 6. Here's the workaround.

Here's the reason: By default, the Parent Paths option is enabled in IIS 5.0, but it is disabled by default in IIS 6.0.

http://support.microsoft.com/kb/332117

Note: I could not recreate the steps below. For me, I had to go back to the ASP Icon and look under the category "Behavior." There I found the option to "Enable Parent Paths."

WORKAROUND
To resolve this problem without changing the application: 1. Click Start, click Administrative Tools, and then click Internet Information Services (IIS) Manager.
2. Double-click your computer name in the left pane, and then double-click Web Sites.
3. Locate the Web site and directory that houses the ASP application.
4. Right-click the application site or directory, and then click Properties.
5. Select Home Directory, and then click Configuration.
6. Click Options, and then click to select the Enable Parent Paths check box.
7. Click OK two times.