Question : SSRS Parameter error

I have a report that has a parameter that the user can enter at run time,everything works great for most users, however..I have one user that when he browses to the report, the parameter entry box is not displayed and he gets the following error:
Reporting Services Error
Parameter validation failed. It is not possible to provide valid values for all parameters. (rsParameterError)

I have checked that he is in the relevant security group etc.. so I just don't know why it's just happening to him, any thoughts?

Answer : SSRS Parameter error

It seems like the user has no access to data needed for parameter (no access to data source).

best regards