I see you are using LogmeIn Hamachi, which is a VPN Host/Client solution that requires the installation of a virtual TAP driver. I have had problems with OpenVPN and WiFi in the past with the TAP v9 driver, I want to add. Try uninstalling Hamachi. As you said 3-5 mins for WiFi to normally work, this is the period of time that Hamachi waits to receive an IP address and defaults to a 169.254.X.X address on the TAP virtual adapter. I am nearly 100% confident that it is Hamachi.
That said, the XPS 1640 is not the best laptop ever-3 stars on Amazon, for example. The HP Probook 4510s, for example, easily surpasses it in value-it runs at about $1,200 here-with 3GB (albeit DDR2, but I think DDR2 vs DDR3 performance is negligible because of other bottlenecks in the system, i.e. Hypertransport and the Intel equivalent that slips my mind, Northbridge-CPU speed, L2/L3 cache, FSB, memory latency, even HDD speed.)
http://www.thebuzzmedia.com/ddr2-800-vs-ddr3-1333-does-speed-matter/ Absolutely no reason to get DDR3 over DDR2 if you have a 1333 MHz 9-9-9-24 DDR3 vs a 1111MHz 4-4-4-12 DDR3, at least in a desktop.
DDR3 has less power consumption, and generate less heat, though, which is good in a laptop.
