Hi there,
the first thing to take into account is that the 1090T, like all other AM3 CPU's doesn't really like running RAM above 1333 Mhz and this could be the reason for your instability when trying to overclock. I would suggest resetting BIOS to Optimized Defaults before you go any further. This should automatically bring your RAM speed down to 1333 MHz and is a much safer option for any Overclocking you wish to do.
The 1090T is a Black Edition CPU so getting more out of it is relatively easy. As a starting point I would disable the Core Performance Boost option (if you have it) and also ALL of the power saving options as they can make things pretty difficult, when it comes to settling a system down. I would suggest, in the beginning, that you leave all voltage options on AUTO and the only thing you really need to adjust is the CPU Clock Ratio. As the 1090T has an Unlocked multiplier, you can freely adjust this from X5 (1000 MHz) - X35 (7000 MHz) the default for the CPU is X16 which equals 3200 MHz. That's all you need for a very quick and easy Overclock. I have had my 1090T running at 4.2 GHz (on air) just by adjusting the Multiplier and leaving everything else alone.
