Firstly, I totally appreciate the time invested to keep this service running (to counter balance previous discussions in this thread).

As a novice, I must admit, I don't understand half the tech language being used here.

However, my attempts to install applications have been unsuccessful in the past few days. Can anyone help?
An install via the App manager fails without a message.
An apt-get install <appname> goes through normal process until a message

An apt-get update seems to go through lots of package libraries but then stumble on

followed by message of invalid signatures: KEYEXPIRED and a suggestion to run apt-get update again.

Is this a configuration issue on my N900. I've head it for 1 year and am really pleased with it.