Weird 2 legged oauth problem

[jlezard]

Hello,

I am using the google api to update some spreadsheets (using 2 leged 
oauth). 
Creating the spreadsheets work fine, creating new worksheets inside a 
spreadsheet also works fine. But I can not seem to interact with the data 
on the spreadsheet....

I get either:

using listFeed

We're sorry, a server error occurred. Please wait a bit and try 
reloading your spreadsheet.

or

using CellFeed

com.google.gdata.util.AuthenticationException

Any ideas, thanks ?