Odd problem with update manager. This has happened about 5 times today so far:

I keep getting a yellow triangle appearing on the top panel that has an exclamation mark in it. When I hover over it, I get the following message:

'The update information is outdated. This may be caused by network problems. Please update manually by clicking on this icon and then selecting 'Check'.'

When I do that, it says there are no updates available, and also that the last time I checked for updates was 7 days ago. However, there were a load of updates installed yesteday, so i'm not quite sure why it's saying that.

About the only thing that's changed lately, is I rebooted my router last night, but I don't think it's caused by that.

Anyone got any ideas?