WGTicon:clearing cookies / cache only works if you have an issue and doing so,. solves it. keep doing it sadly, won't work. I haven't cleared my cache/cookies in 6 month, so it's not a panacea.
And some say a leopard can't change its spots.
To the OP, I use Maxthon and usually have a smooth meter.
You did mention the virus and malware scanners - are they running in the background when playing. I know Norton used to kill my meter (in fact slowed the whole machine down).
Speaking of running, do you keep an eye on your CPU usage? Maxthon has a CPU usage built in...if it increases I wait till it drops. I used to use a standalone CPU Usage program that I could overlay using full screen (downside of maxthons is you lose this in full screen).
As Icon said, it could also be the version of flash and Chrome users have problems with Pepper Flash....I know Scotthope has links to resolve this.