Question : Exchange Calendar

I am using Exchange 2007 and Microsoft Outlook 2007. I am having an issue with two computers sharing their calendars. Example: If comp A is changing comp B's calendar, computer B can sometimes see the changes and sometimes cannot see the changes.
I have checked the sharing permissions and comp A and comp B both have permissions to each other's calendars to make changes. I have also made sure that both comps are connected to the network so they can communicate.

Why can they sometimes see the changes and sometimes cannot on the calendar?

Answer : Exchange Calendar

I'm using windows 7 ent;64bit on a HP notebook, whithout any single lockout or BSD (Blue Suddin Death) for more than 8 months, sometimes I leave it running for more than one week  in the office and access it remotly ( ok I'm too lazy to un plug and carry it every day :) )
I'm almost certain that it is related to hardware driver 64 bit compatability, specially network cards