Here's some info on the ROBUST PLAN option from BOL:
ROBUST PLAN
Forces the query optimizer to attempt a plan that works for the maximum potential row size, possibly at the expense of performance. When the query is processed, intermediate tables and operators may need to store and process rows that are wider than any of the input rows. The rows may be so wide that, in some cases, the particular operator cannot process the row. If this happens, SQL Server produces an error during query execution. By using ROBUST PLAN, you instruct the query optimizer not to consider any query plans that may encounter this problem.