I noticed it during Gnome 2.17. Then I thougth it got solved in 2.18.0 but it dosn't seems so.

Juerg told me that it has something to do with Flash9 once. I'm using the final now and did a clean install cos of that.

I may have to write down the situations when the freezes accour. Might be a problem with the 32bit version.

I'm having the problem on the 64 bit version and with sfwdec installed instead of flash.
I suppose is something to do with the disk access (I thought something related with gvfs 2.0) , but I'm pretty a newbie.