Re: Huge problems with Adobe Flash 10.2.152.27
Disabling hardware acceleration probably slows it even more.
I found that using the libgcflashplayer.so implementation of flash from google chrome (unstable) works well (can be used in any browser, i use it in Opera). They have a special version, 10.2 r154 flash included with that browser.
Just link it to your $HOME/.mozilla/plugins/ folder (from its location - /opt/google/chrome/) and delete any other flash plugins.