merge client failing

Hi

We have sql2005 merge replication happening - it is using replisapi.dll over the net.

One of the clients has been working fine, until yesterday afternoon - we are running sql2005 sp1 at subscriber and distributer

The message is as follows....

Please help !

Error messages:

The process could not read the request message due to OS error 10054. (Source: MSSQL_REPL, Error number: MSSQL_REPL-2147014842)
Get help: http://help/MSSQL_REPL-2147014842

The format of a message during Web synchronization was invalid. Ensure that replication components are properly configured at the Web server. (Source: MSSQL_REPL, Error number: MSSQL_REPL-2147199374)
Get help: http://help/MSSQL_REPL-2147199374

The subscription to publication 'yarraman main' could not be verified. Ensure that all Merge Agent command line parameters are specified correctly and that the subscription is correctly configured. If the Publisher no longer has information about this subscription, drop and recreate the subscription. (Source: MSSQL_REPL, Error number: MSSQL_REPL-2147201019)
Get help: http://help/MSSQL_REPL-2147201019

OS error 10054 is "An existing connection was forcibly closed by the remote host.", which could mean security or network issue. Could this be the case?