Transport Layer NONE on Interface configuration

I have two PCs each with a different Matlab version. First PC has version 2010a, second has 2010b. I have developped a target inherited from ert.tlc. Even if I use the same target on both PCs there is a difference in Parameter Configuration which makes it imposible to use external mode in PC with version 2010b.

In PC with version 2010a in Parameter Configuration->Real-Time Workshop->Interface, Transport Layer _is by default _tcp/ip _and MEX file is _ext_comm. In Pc whit version 2010b Transport Layer is none and is unchangeable and there is no MEX file. I have searched for ext_comm in PC with version 2010b and it exists but it seems to me that matlab cannot find it.

Does the problem exist because of the version difference or could it be anything else?