*Online index operations are available only in SQL Server Enterprise, Developer, and Evaluation editions
This is true till sql server 2008 R2 from Denali – sql server 2012 we could able to re-index online for varchar(max) as well.
“Online index operation cannot be performed for index ‘XXX_PK’ because the index contains column ‘xxx’ of data type text, ntext, image, varchar(max), nvarchar(max), varbinary(max) or xml. For non-clustered index the column could be an include column of the index, for clustered index it could be any column of the table. In case of drop_existing the column could be part of new or old index. The operation must be performed offline.”. Possible failure reasons: Problems with the query, “ResultSet” property not set correctly, parameters not set correctly, or connection not established correctly.
To overcome make these types of index offline.