Error on Simulink for a xpc target

I have a xpc target and I am writing s functions in the simulink to load data and read data back from the add on card on the xpc target. When i am trying to connect to the xpc box and run the simulation after it gets connected i get this error:external mode open protocol start command failed.

I have a toworkspace block that is causing this. I am trying to read out 258 MB of data. Is this a limitation? what are the other ways to read out the data.

[Kaustubha Govind]

Mohammed: It is possible that this is a bug. Perhaps you could try contacting MathWorks Tech Support about this?