I agree with the post above. I often have clients who are afraid to have multiple recommenders from a single job. This is not, in and of itself, a weakness. If you have only had only one job this might be your only option and it is perfectly okay. In fact, if you have been at a job for more than two years, it might not make sense to go back and ask someone from your old job. The information a former employer would provide might not be current and provide a clear snapshot of who you are today.
If you are asking recommenders from the same company, the key will be to ask individuals who can provide different perspectives. For example, in addition to your supervisor, you will ask the individual that you work with cross-functionally on a special project. Or you will ask the manager that you interact with as part of your recruiting efforts.
Hope this was of help!
Conrad and the Stacy Blackman
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Stacy Blackman | Stacy Blackman Consulting Inc | http://www.StacyBlackman.com | +1 323.934.3936
MBA blogger, US News and Author, The MBA Application Roadmap