I use an USB wifi adapter based on Ralink RT5370 chip:

$ lsusb

Bus 001 Device 002: ID 148f:5370 Ralink Technology, Corp. RT5370 Wireless
Adapter

Immediately after boot, network works fine, but after some time all network
communication ceases and an endless stream of messages like this keeps filling
dmesg:

kernel: ieee80211 phy0: rt2x00usb_vendor_request: Error - Vendor Request 0x07
failed for offset 0x7010 with error -110
kernel: ieee80211 phy0: rt2x00usb_vendor_request: Error - Vendor Request 0x06
failed for offset 0x7010 with error -110
kernel: ieee80211 phy0: rt2x00usb_vendor_request: Error - Vendor Request 0x06
failed for offset 0x0404 with error -110

After rebooting, I can again use the network for some time, but soon the
problem reappears.

Interesting thing is that this only happens if the system has 10 GB RAM. My
system has 2x1GB plus 2x4GB DIMMs, and when I remove one of the 4 GB DIMMs
(thus reducing the amount of memory to 6 GB) the problem does not appear. To
rule out the possibility of bad DIMM I have run memtest86 for several hours
without finding any problems, also the system is rock solid with 10 GB RAM when
I remove the USB wireless adapter and use wired Ethernet.

Version information:
$ uname -a
Linux susa 4.1.13-5-default #1 SMP PREEMPT Thu Nov 26 16:35:17 UTC 2015
(49475c3) x86_64 x86_64 x86_64 GNU/Linux
$ /usr/sbin/modinfo rt2x00usb
filename:      
/lib/modules/4.1.13-5-default/kernel/drivers/net/wireless/rt2x00/rt2x00usb.ko
license:        GPL
description:    rt2x00 usb library
version:        2.3.0
author:         http://rt2x00.serialmonkey.com
srcversion:     3F336708588FABE8A5041C1
depends:        usbcore,rt2x00lib,mac80211
intree:         Y
vermagic:       4.1.13-5-default SMP preempt mod_unload modversions 
signer:         openSUSE Secure Boot Signkey
sig_key:        03:32:FA:9C:BF:0D:88:BF:21:92:4B:0D:E8:2A:09:A5:4D:5D:EF:C8
sig_hashalgo:   sha256