CVS: replace from head error

[Deepak Sable]

Hi ,

I am using Eclipse 3.0 and from Eclipse I am accessing CVS.But when i try to 
replace 
from head ,I get an error as below.


I/O has been interrupted.
  The most likely cause of the interrupt is either an intermittent network 
failure or a communications timeout.
  The CVS communications timeout can be adjusted in the Team/CVS preferences.
  Another possible cause is the improper configuration of the "ext" connection 
method.
  The "ext" connection method can be configured on the Team/CVS/EXT Connection 
Method preference page



Also wanted to know what does,
 update 
 Synchronize with repository
 replace do?



Thanks in advance
Deepak