SBS 2008 daily report emails no longer working (reports themselves are okay)

Ok I'm stumped. I applied hotfixes last week (all of them; prior to last week the server was fully patched) and, since then, daily reports are no longer emailed automatically. All  my SBS 2011 boxes are fine but this is the only SBS 2008 box we have left so we've nothing for comparison.

The monitoring database is fine I believe, and if I manually run the report it's emailed okay.

Account SBSMonAcc *was* disabled (not by me) but I've re-enabled it.

This is logged in the MonitoringServiceLogs file:

2012-10-15T08:15:00.011348 : Logger started at: 2012-10-15T08:15
2012-10-15T08:15:00.011348 : ***************** Starting GenerateMonitoringReport task... *****************
2012-10-15T08:15:00.011348 : Generating Shore Laminates Server Backup...
2012-10-15T08:15:00.260948 : XML generated...
2012-10-15T08:15:00.323348 : HTML generated...
2012-10-15T08:15:00.323348 : Report stored in archives...
2012-10-15T08:15:12.350948 : Failed to send report email.
2012-10-15T08:15:12.350948 : Generating Shore Laminates Server Backup finished.
2012-10-15T08:15:12.350948 : ***************** GenerateMonitoringReport task finished. *****************

and this is logged in Event Viewer

Inbound authentication failed with error LogonDenied for Receive connector Default SLNSRV. The authentication mechanism is Ntlm. The source IP address of the client who tried to authenticate to Microsoft Exchange is [192.168.7.2].

Everything on the receive connector looks the same as it is on our SBS 2011 boxes.

Any ideas?

Many thanks,

Jim