Np,
By the way we are aware that there are many problem with CC2538 and Contiki. You are also likely to run into them as you proceed. We are working with the cc2538 business unit to fix these usability issues.
You can search through the forums for some of these problems you would encounter. If you do run the problem of loading the file seems stuck towards the end, there is a work around: replace the <uniflash install>\uniflashv3\ccs_base\emulation\cc2538.gel file contents in with this one http://e2e.ti.com/cfs-file.ashx/__key/communityserver-discussions-components-files/81/1602.cc2538.gel
For history and detail, you can look through this thread if you want when you encounter the problem. http://e2e.ti.com/support/development_tools/code_composer_studio/f/81/p/239320/1105956.aspx#1105956
Victor