Because I don't know how to notify you else; I do it this way:
There is a bug in the wireless implementation: the Yun does not work with networks with spaces in their ssid. I have tested this on our corporate network and I could not get it to work until I changed the ssid in something without spaces.
Just thought I'd better share this, as it cost me a few hours (of my life 
to find out.
Thomas
I test it and it works, No bug.
A valid SSID is 0-32 octets with arbitrary contents (Section 7.3.2.1 of the 802.11-2007 specification) . The space in SSID is valid.
My test case is this:
Access point is Cisco WAP321 with multiple ssid's.
I tried "The Protocol Room Office" and it does not work.
Added an ssid named "devnet" to the ap and it works.
Tried and tested multiple times.
I test with TP-link OEM firmware as well as Openwrt firmware, and both worked fine. Plus IEEE spec. You might need submit bug report to Cisco.