I have same problem. For me, work-around is to remove and reinsert rtl8723be module:
root@lenovob5400# rmmod rtl8723be && modprobe rtl8723be
Sure it's not a solution, but better than rebooting.
What a shame Ubuntu does not work with such popular wifi card.
BTW, I tried kernel 3.15, but it has same issue (and few others).
Looking forward for better solution. Go get it hackers! ;-)
Update:
Friends, please vote on related ubuntu bug.
Update 2:
Upcoming ubuntu kernel 3.13.0-25.47 have #1240940 bug fixed,
however, after installing this kernel from ppa, the rtl8723be module is there indeed, but I was not able to connect at all.
Currently I am using standard 3.13.0-24-generic kernel with rtl8723be kernel module from:
https://github.com/lwfinger/rtl8723be.git at 604aa9058fb9e5bb1cf571c99989d081f8fc8b9b commit.
Update 3:
I tried ndiswrapper 1.9 with winxp 64 drivers (and man others). All failed to load:
[ 327.503426] ndiswrapper version 1.59 loaded (smp=yes, preempt=no)
[ 327.517958] ndiswrapper: driver netrtwlane (Realtek Semiconductor Corp.,08/02/2013,2010.5.0724.2013) loaded
[ 327.519049] ndiswrapper (NdisWriteErrorLogEntry:188): log: C0001388, count: 1, return_address: ffffffffa05e5d9f
[ 327.519052] ndiswrapper (NdisWriteErrorLogEntry:191): code: 0x605
[ 327.519143] ndiswrapper (mp_init:211): couldn't initialize device: C001001E
[ 327.519146] ndiswrapper (pnp_start_device:395): Windows driver couldn't initialize the device (C0000001)
[ 327.519150] ndiswrapper (mp_halt:254): device ffff8800cd747880 is not initialized - not halting
[ 327.519151] ndiswrapper: device eth%d removed
[ 327.519380] ndiswrapper: probe of 0000:04:00.0 failed with error -22
I tried one more trick - added fwlps=0 parameter for the rtl8723be module.
So far so good. We will see...