I have an E545 and my wireless networking card is extremely flaky (30sec of connectivity, 2 minutes of connecting at the worst; 30min connected, hours of the prior at the best). I've tried updating drivers, reseating it, &c and nothing works. I got a replacement card from an old Dell Latitude, put it in and got: "1802 - Unauthorized network card"
http://support.lenovo.com/us/en/documents/ht001309
Their FCC excuse is utterly laughable because other manufactures don't require their computers to have white listed parts.
I wish I knew how low the Thinkpad brand has sunk under Lenovo before buying this machine. So, just a PSA to others out there. Lenovo is no friend of yours.
See: https://en.wikipedia.org/wiki/ThinkPad#Use_in_space
Over time, alternative bios's with different whitelists often become available for Thinkpads. Not sure if this will live through UEFI.
Good luck.