BadEnumeration while iterating over sharepoint list fields

I'm try开发者_StackOverflowing to insert a bunch of data into a SharePoint list. The List is a custom list based on the Item content type with a couple of custom columns, Contact and Code, where code is a custom field type based on SPFieldText.

I am exploring the list using PowerShell 2.0, and enumerating the fields of the list (or any given list item) causes an exception as follows:

PS C:\> $list.Fields

# output of a few fields

An error occurred while enumerating through a collection: Exception has been thrown by the target of an i
nvocation..
At line:1 char:7
+ $list. <<<< Fields
    + CategoryInfo          : InvalidOperation: (Microsoft.Share...on+SPEnumerator:SPEnumerator) [], Run 
   timeException
    + FullyQualifiedErrorId : BadEnumeration

I don't really get why this is the case - nothing on the site seems to be broken, and SharePoint Manager is able to enumerate all the fields and list items without a problem. Further, when I try to grab a single list item and inspect its fields, I get null from my custom field:

PS C:\> $list.Items[0]["Contact"]
2;#Collins, Ben

_______________________________________________________________________________________
PS C:\> $list.Items[0]["Code"]

_______________________________________________________________________________________
PS C:\> $list.Items[0]["Code"] -eq $null
True

The "Code" field in the list doesn't actually have a null value, so I'm at a bit of a loss. Anyone know what might be going on?

Turns out the feature containing this field type wasn't activated (the list had already been created, and I've been making changes to the feature).

Doh.