You run a report in Reporting Services which subsequentially fails with error RDlObjectModel is not a member of ReportServices. You investigate the suspect textbox and find an expression in the textbox contains the following code Microsoft.ReportingServices.RdlObjectModel.ExpressionParser.VBFunctions. This appears to happen when you copy and paste a text box that contains and expression.
A connect case is available here http://connect.microsoft.com/SQLServer/feedback/details/757358/pasting-objects-with-expressions-pastes-fully-qualified-functions but for now you will need to manually strip the expression of this code. Either do this manually within your textbox expression or open the report in View Code mode and search and replace.