Hello all,
Long time listener, first time caller.  I've got a DIR-655 which has been running flawlessly since I got it almost two years ago.  I got it to replace an old Linksys 4 port router, which I extended using a Linksys SD2008 GB switch.  When I got rid of the Linksys router and installed the 655, I couldn't get an IP on any device through the SD2008.  I'm back at it, trying to get this to work with no luck.  I get link lights on all connections, I've tried crossover and straight through cables (besides the fact that the 655 auto-negotiates the connections), and both devices are within 2 feet of each other.  I think I've eliminated the physical layer as the source of the problem.  
Any ideas?  
Thanks in advance.