Why can't I withdraw any BTC from MtGox?
When Mt. Gox initiates the demand for verification your account is essentially frozen for withdrawals until you send in the required identification (color photo ID and whatever else they want) and your account gets verified.

The instructions from the link you provided will clearly state what is needed.  

For example, it might state


  
  VALID Photo ID Proof (Identity card, license, passport,...)
  Residence Proof (utility bill, tax return, insurance,...)
  ISSUED WITHIN 6 MONTHS
  


For the color photo ID, even a pic of the ID taken with a phone is usually sufficient.