MSP 2010 wont let me baseline project

Hi All,

MSP 2010 will not let me set the entire project as a baseline. Ive tried it by selecting the entire project check box as well as highlighting all tasks then checking 'selected tasks'. It will let me assign a baseline if I select only a few tasks but thats it. My plan has 2500 tasks. I tired selecting 500 tasks but it wouldn't do this either.

Any ideas greatly appreciated as you can imagine this is causing me some frustration.

Cheers

Steve