Using data source to update user defaults

Question

I have a default entry in my user defaults that is a list. Each item of the list is a list of records. I use the following code to delete an entry.
on deletePlaylist()
set tableView to table view "Playlist" of scroll view "Playlist" of window "Schedule Window"
set selectedDataRows to selected data rows of tableView
if (count of selectedDataRows) > 0 then
delete (item 1 of selectedDataRows)
set contents of default entry "specialList" of user defaults to contents of data source "Specials"
register
end if
end deletePlaylist
This code seems to work; when I open my plist the entry looks just as it should. The problem is that the next time I open my program, I get a 1728 error when I try to read that default entry.

Answer 1

I'm not using pipes anyplace in my program.
I'm reading my user defaults like this
set theList to contents of default entry "specialList" of user defaults
tell data source "Specials"
set update views to false
delete every data row
repeat with a from 1 to length of theList
set theRow to make new data row at end of data rows
tell theRow
set contents of data cell "thisDay" to thisDay of item a of theList
set contents of data cell "thisTime" to thisTime of item a of theList
set contents of data cell "thisFinalPlay" to thisFinalPlay of item a of theList
set contents of data cell "thisPlaylist" to thisPlaylist of item a of theList
end tell
end repeat
set update views to true
end tell
I'm writing my user defaults like this in my delete routine.
delete (item 1 of selectedDataRows)
set theList to content of data source "Specials" --I think this is the problem line
set contents of default entry "specialList" of user defaults to theList
When I open my plist in Property List editor, the pipes do not show. The entries are identical to those in the plist before it is screwed up. I think that when my program asks for user default thisList it is actually finding |thsList|. Does that make sense?
When I add to the data source, I make the changes to theList and then rebuild the data source and write theList to user defaults. This works fine.
If I could get the line number of the selected data row in the table view, I could use that index to delete the appropriate item from theList and then write theList directly to user defaults like I do when I add to the data source.