SQL Server Service seems stuck
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I'm running a stored procedure and it just doesn't finish. Here are a couple of things I have noticed:

* Normally, the procedure takes 20mins but now it's running for over an hour by now.
* Normally, the procedure uses several cores to process but now it's using just one. 
* Normally, the procedure shovels around 10+ MB/s ( sometimes 100+ ) but now it's not shoveling any data.

The stored procedure is suppose add some data to a big table ( that's done ), to calculate some mean values into a small table ( that's done ) and to calculate some standard deviations ( seems to stuck be here ).

What are the things I can do? Or what are the things I can investigate.

I'm the only user on the server ( it's a remote machine ). I'm running from inside the MS Management Studio. The version I'm running is SQL Server 2008 R2.

Thanks in advance,
Christian