Event ID: 15113
Warning message: ISA Server disconnected from the following client: IP because its connection limit was exceeded.
Config: Windows SBS 2003; ISA 2004, standard; less than 30 computers. The default setting on ths ISA is already 160 (Connection limit per client).
No sure if this article would help: http://support.microsoft.com/kb/927099?wa=wsignin1.0. It doesn't make sense that changing the number here will help, does it?