Mavericks causing wi-fi, internet connections problems on BT router
I use an MBP and have upgraded to Mavericks. I have a BT account and use the BT router supplied. I have a Time Capsule connected to the BT router and TPLink range extenders. The household has 2 PCs, 1 iPod and 2 iPhones in addition to my MBP. All work perfectly except for the MBP that now has to be used with an ethernet cable plugged into the TPLink extender. The problem is with Mavericks because re-booting with Mountain Lion restores the wi-fi, internet functionality.
The problem is seen by either no wi-fi connection, exclamation mark in wi-fi symbol at the top of the screen, or a normal symbol but no internet connection, red lights shown in the diagnostic assist me box.
I have had the MBP checked out by the Genius Bar and it is OK, the wi-fi worked in the shop so it seems to me that something has been altered that causes issues with BT routers. It has been suggested that ISP supplied routers are poor quality and I should buy another one but I thought that the Time Capsule acted as a router so I'm not sure that this is a valid suggestion.
I know that other people have had similar problems and I've tried all the resetting, erasing and remaking network ideas, caffeinating and so on but all to no avail.
I'd be interested to hear if anyone out there has experienced similar issues and more particularly has found a solution.
MacBook Pro, Mac OS X (10.6.7)