Watch this and see if it is what you are talking about.
http://www.youtube.com/watch?v=bLG6clch2RY

Also read this.
http://support.microsoft.com/kb/291621

Are you using Calendar Groups Like in this article? If not can you be more specific about the issue. Which scheduling window are you referring to?
http://blogs.msdn.com/b/mvpawardprog...look-2010.aspx

Also are both of the accounts using an Exchange server? If so each account must publish their free/busy information. Click File > Options > Calendar Options > Free/Busy Options. Also you can't have the month value for publishing set to zero.