When you’re building a WebPart that uses some of the ASP.NET validator controls, make sure you specify a validation group for all of them and for the Control firing the validation (i.e. the Submit button). Also, if you’re using a validation summary specify it’s validation group property too.
If you don’t do this, the validation might be fired by other controls rendered by SharePoint preventing you to navigate away from the page. I just ran into this since I created a new Page in a Publishing site. I added my WebPart to this Page and then I wanted to Publish the page. The “Submit for Approval” control in the “Page Editing Toolbar” fired the validation so I had to fill in all my required fields first in order to be able to enter the approval process.
So, I think it’s a best-practice to always use ValidationGroup inside of WebParts.
