I select 'Tools | Compare | Data Compare' in Toad for Data 2.6 (or Toad for SQL Server 5.0) on SQL Server table with over 200 columns.
Once the compare result came back, the result has over 400 columns. I right-click and select "Export to Excel" and gets the following error before Toad for Data Analyst (or Toad for SQL Server) disappears.
Select relevant columns to compare during the 'Select Column' window of the Compare Wizard and get the number of columns below 256.
Waiting for fix in a future release of Toad for Data Analyst and Toad for SQL Server.