Questions and problems of new version (1.00.851)

I come from old Bs and found some changes in the new version.
First of all DivX options are no more selectable in the Preferences menu, not even when playing DivX files.
Ac3 filter is no more available under filters, not even when playing ac3 file, and using "Options->Filters" (i use the sourceforge one, often listed on this forum too)
Reproduction of some heavy res movies (in DivX coding) is heavier then in previous version of BS, and results in non smooth playing.
Is this a known issue?
I tried every rendering method available:
RGB, every overlay, and neighter too.
Always the same: BS sucks up to 65% of CPU (from XP's task manager), and reproduction sometimes even halts, loosing frames, while beeing generally not smooth.
Am i alone in experiencing this?