Based on the number of related issues and even though this is a Raspberry Pi B+ I am going to have to say this is highly likely related to power issues.
Power issues on the Raspberry Pi are often not consistent, for example, the Raspberry Pi will operate without issue for minutes, hours, days, etc. Before failing.
Please unplug everything and check the power test points.
It's also worth noting that USB power plugs often fail to supply the require 5 V EVEN if they are rated as such. If the PSU is providing the correct voltage the cable may be losing enough to cause the Raspberry Pi problems (I have had direct experience of this, do not buy cheap USB cables).
My own experiments showed that a difference of just 0.15 V (average) was enough to cause sporadic stability issues, that would affect the image on the SD card.
The PiHUB (again, in my experience) seems to offer superior power consistency and improved stability.