Portal field not modifiable
I have a new problem with my database and I'm having trouble tracking it down. I have a portal field within my Firms layout for Contacts (related table). This has worked just fine in the past, but today when I click into the first blank row to create a new contact (which I have confirmed is allowed based on the relationship) it says "The action cannot be performed because this field is not modifiable." It's a simple text field without any validation. I've turned indexing on and off and that doesn't make a difference. I've turned off the related script triggers and that didn't make a difference.
Where else might I try looking to isolate the problem?