Sudden, unexplainable drop in hash rate

[LobsterMan]

I've been running bitcoin for a few weeks on my windows 7 machine now. With my i7 processor I was getting around 6000 khash/s pretty consistently (using only CPU generation). Then I started messing around with trying to compile the source in both Visual Studio and MinGW. I was only successful in building openssl and wxwidgets with mingw, my attempts with the berkeley db library failed, and I didn't really try with boost; I was also largely unsuccessful thus far with visual studio. I did briefly try running puddinpop's cuda client, first the cracked one and then to compare performance, his last "official" release with auto-donation feature. It was sometime after this that I noticed my cpu-only hash rate had now fallen to only around 4000 khash/sec.

I've tried rebooting my machine several times, I've even deleted the precompiled binary and removed the files from my %APPDATA% folder and started over again with a fresh install (redownloaded all the blocks) without any success. I have tried changing the throttling settings with respect to limiting the number of cores without being able to reach my previous calculation rate. I have even tried stopping all non-system-critical services to see if that was having any impact, but previously with my higher hashrate, I was not operating with a minimal set of processes.

I'm pretty stumped as to what would cause this fairly dramatic decrease in performance. Someone in IRC was thinking that if the win32 stock binary doesn't have statically linked libraries I may have broken something while messing around with compilation, is this possible?

I suppose it's also possible that one of the other clients I tried have somehow affected performance, or left something undesirable behind which are stealthily eating up some of my cpu cycles...

At this point I'm kind of at a loss and I'm hoping someone can offer some insight or advice as to what may have caused this?

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[Ground Loop]

Are your settings still showing an unlimited number of Cores for generation?

Could it be you were faster when you enabled fewer cores?  (I know some of my HT machines behave this way.)

What does your Resource Monitor show?  All CPU's 100% loaded?
Any changes to system cooling?

[LobsterMan]

Are your settings still showing an unlimited number of Cores for generation?

Could it be you were faster when you enabled fewer cores?  (I know some of my HT machines behave this way.)

What does your Resource Monitor show?  All CPU's 100% loaded?
Any changes to system cooling?

I've played around with the cpu limit restrictions to no avail, cpu perfmon shows 100% load on all cores, and nothing has changed with my cooling  

The only possible change....although it may have always been this way and I just never noticed it, is that there seems to be a slight increase in kernel cpu times if I enable that checkbox from task manager on the performance tab, sometimes I see red spikes which I'm not too sure to make of (but like I said, it may have always been like this):



Notice the green line at the very top of the CPU usage graphs indicates full usage on all cores...although it does seem to dip slightly when my client receives a new block.