Activity Monitor error

Hi,

I just started activity monitor on sql server 2008 standard edition X64. When I clicked processes, after some delay there is error message:

The activity monitor is unable to execute queries against server abc. ........ Arithmetic overflow error converting expression to data type int. (Micorsoft SQL Server, Error: 8115).

"Microsoft SQL Server 2008 (SP3) - 10.0.5500.0 (X64)   Sep 21 2011 22:45:45   Copyright (c) 1988-2008 Microsoft Corporation  Standard Edition (64-bit) on Windows NT 6.1 <X64> (Build 7600: )"

How to resolve this issue, please help.

Thanks