You should be using the latest driver.
Increased fan usage could be due to bug fixes - you'll have to ask NVidia about that.
I have the same issue in Photoshop CS6. The brush circle appears normal when set to a relatively small size, but as I gradually increase its size using the right square bracket key, the circle begins to appear incomplete, with more of the circle becoming missing as I increase size, before disappearing altogether as I set it ever larger. The Clone Stamp, Healing Brush and Spot-Healing Brush also behave in the same way. Did you also notice that if you moved a selection within an open file, it would usually cause traces of the marching ants to remain on the screen in its former position?
However, the driver I have installed (18.104.22.16834) for my Nvidia GeForce6100 nForce405 graphics card is dated 8/7/2009, which is later than spring 2009, the point when the bug is supposed to have been fixed.
I know my Nvidia graphics card is not officially supported with Photoshop CS6, and I noticed that with the Graphics Acceleraton option ticked in Photoshop CS6, an open file would appear very slightly blurry at certain magnifications. Unticking the acceleration option cured this, but I still have the above issues, the new Blur filters are not adjustable via the on-screen dial method (limited to the conventional sliders only) and I am also unable to open video files, it seems. It just hangs. When I cancel, I get a message saying something like 'could not complete your request because the DynamicLink media server is not available'. I can, however, play video files without a problem in Bridge CS6.
I am using Windows XP, SP3.
Chris - I appreciate I should in theory be using the latest driver but the fan usage did seem rather excessive so I may try another older but post-2009 driver to see what happens.
Page D - Yep, my card isn't officially supported by CS6 either - I notice the driver 306.81 I tried shows as being compatible with your card too - you could try it & see what you think as it did at least solve the brush problem. I may try another less recent driver too as a short term fix. If you're not happy with it, to roll back to your original driver, I found system restore was the easiest method.
However, in the long-run, support for XP from Microsoft runs out in early 2014 I beleive so I think before then I'll be looking at getting a newer PC
The worry, for me, Les, about updating the graphics card driver is that you hear all sorts of anecdotes about people updating these things, and then getting into a heap of bother with other issues cropping up. And, crucially, if I did encounter problems with a newer driver, such as your one, I'm not sure I can revert back to my current driver, because since I had my internal hard drive replaced, I can no longer use the System Restore facility. Also, the 'Roll Back' option may not be open to me either, because of the internal hard drive replacement, and, if so, I would only know this after I updated the driver, in which case, I'm stuck with the newer driver, without being able to roll back. That is when I would be in a right pickle (don't know if you've heard that expression, but here in the UK it means 'mess'!). It may be a case of 'Better the devil you know'.
Most of the issues I've spoken about, are not that problematic to me, thanks to the clone source overlay, the ability to remove the traces of marching ants by turning the layer's visibility off and then on again, the new Blur filters also still being controllable with the conventional sliders, and not really wanting to use video files with Photoshop CS6 (I have Premiere Elements 8, for that).
I will probably just continue to persevere with it!
the fan usage did seem rather excessive so I may try another older but post-2009 driver to see what happens.
Did you monitor the temperatures of your video card? It's possible it actually NEEDS to run those fans faster to keep the chips at a safe temperature.
There's a free program called GPU-Z (I'm sure among others) that will do the job.
I have just discovered that I no longer have the problem of a disappearing brush circle when enlarging it beyond a certain size (which also affected the Clone Stamp, the Healing Brush and Spot Healing Brush). A quick check in Device Manager shows that, unbeknown to me, a driver update for my NVIDIA card (now showing version 22.214.171.1243, driver date 31/1/2013) was automatically installed, presumeably very recently, as I have only just noticed the brush circle now working properly.
I still do not have the function of the Blur Gallery's on-image 'dial' adjustment, though, and it remains the case that I can only adjust via the sliders on the right-hand side of the screen. Also, I still get traces of the marquee and the corner handles/side handles in their former positions on-screen, when moving a marquee I have placed on an image, via the Move Tool. I assume these are seperate issues, and not caused by any NVIDIA driver incompatablility(?).