Is it possible that an airport express could go out in less than 6 months.
The new airport express I purchased when you were last out does not show on the network after I reset it and try to extend the network.  The light on the express is blinking yellow? Let me know if its something I'm doing or if you think the airport express on out?

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It's extremely unlikely that the airport express has failed.  The failure rate on that hardware is very very low.  So I have a good bit of faith in it.  There must be something else.  If you've done a hard reset on it and had it to rejoin your network and you feel you've done everything correctly then there may be something we're missing.  Luckily the airport utility will tell us what the problem is.  Launch airport utility and double click on the express icon in the left hand column.  When the next window appears, click on the yellow dot next to Status.  That should show you a list of errors the airport express is reporting.  Then we can go from there.