I wonder if you're not giving up too quickly... what does `dmesg` indicate? syslog?

Also, when you say you reflashed.. you reflashed rootfs? did you restore anything? I ask because you could easily be having an issue with the modules (/lib/modules)

if it really is hardware, most likely going on IRC will let you contact those who know the N900 very well, and who might be able to help you hunt down the offending hardware. you might just find it's a silly thing, eg lost magnet, lol