CyanogenMod ROMs have that problem. It's not kernel related I think.When I turn wifi on my phone reboots. I posted a last_kmsg awhile back, but just looked at it and I posted a last_kmsg from my Nexus 7...Oops.
Here's one from today. I'm on CM9 9/4 nightly ROM.
http://dl.dropbox.com/u/7376317/last_kmsg_htc.txt
It doesn't happen every time you turn wifi on though. Just randomly.
Sent from my HTC Sensation using Tapatalk 2