When attempting to insert a custom list form in SharePoint Designer the form never displays in design view. There is no error message, and the form never gets inserted into the page.
There may be multiple causes. Thus far, we've identified that it can occur because of a failed SP1 install for MOSS. If you take a look at the Netmon traffic and compare it to a healthy server all you'll notice it is missing SOAP calls. Note: The other thing that is odd about this issue is that all SPD users will experience it.
Method 1 - Fix the failed upgrade.
You'll need to reinstall SP1 using our recommendations:
Method 2 - Clean up the user profile.
You'll need to clean up the user profile using these steps: