Sadly, Lenovo cannot be relied on as they once were (even for the first few years post-IBM). My W520 has been to warranty depot three times - still not fixed - for this problem that has been known for 1.5 years:
http://forums.lenovo.com/t5/W-Series-ThinkPad-Laptops/W520-s...
I'm still using, and loving, my T61P. If only there was a way to get an i5 or i7 in that lovely reliable chassis :(