could not generate a list of fields for the query. check the query syntax, or click refresh fields on the query toolbar error message in ssrs 2005

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Hi,

When I am trying to add one data set into SSRS 2005, I am getting above message and then if I try to preview the report i am getting "System.OutOfMemoryException was thrown" error message.

Please suggest me what is causing this issue ASAP. Thanks for the help in advance.