SQL/Access ODBC error 3157

I have been asked to look at some client PCs that run an Access front end to an SQL database. Occasionally, the client will crash with the following details:

Run-time error 3157
ODBC - Update on a linked table 'communications failed'
ODBC-SQL Server Driver Timeout expired #0

The driver version in question is: 3.70.08.20 (23/10/99)
--
It appears to be more common on certain client PCs and on certain records. Usually, when trying to add new details attached to that particular lookup.The SQL server is running 7.00.623

All I have managed to find so far is various decriptions of the error, but as yet no solution.

Thanks