Thank you Daniel that seems to have worked.
I added the two extra variables to the omnirc file (OB2SHMIPC=0, OB2INETTIMEOUT=10) on the exchange servers.
OB2IPCKEEPALIVE=1
OB2IPCKEEALIVETIME=900
OB2IPCKEEPALIVEINTERVAL=60
OB2SHMIPC=0
OB2INETTIMEOUT=10
Thanks again for your help.
Adam