BEX is a "Buffer Overflow Exception", it is related to DEP which is "Data Execution Prevention".
The GameOverlayRenderer is the Steam overlay (I think it is, but I don't know why it needs to run for the launcher). I've noticed that even if you turn off the overlay in the Steam properties for the game the overlay does not turn off. Try turning it off anyway, see if that helps.
See http://technet.microsoft.com/en-us/library/cc738483%28WS.10%29.aspx for more info on DEP and BEX.
You could try turning off DEP for the launcher and/or the FNV game executable itself.
right click on my computer
go to properties
click on advanced system settings
under performance, click settings
click the Data Execution Prevention tab, and then click Turn on DEP for all programs and services except those I select.
click Add, browse to the executable file for the program and add it.
You might also add the program "iexplore.exe" to the DEP exclusion list as well. I personally think that's unwise because it could allow malware to get on your computer through the Windows Internet Explorer (that's the iexplore.exe) when DEP is turned off.