4.5.6 -> 5.0.8 slowness problems

[Meowmixjinx]

our 4.5.6 email server crashed, and we went 5.0.8 for our rebuild, and ive noticed some awful increases in certain load times.
it is nearly impossible to create a new user via the administrator interface, it takes 15 seconds for the text that i type to show up in that window.
moving files from an inbox to a folder and other operations have become nearly unusable, while other operations have increased considerably in speed.

is there anyway to fix these or anyway to figure out whats causing them?

ive looked for /opt/zimbra/log/zimbrastats.csv but that file doesnt appear to exist.

server is a dual 2.0ghz xeon with 2GB ram
and 3 146 10k rpm SCSI hds in raid 5,
running suse 10.2

[Meowmixjinx]

just some carification it looks like, its somehow related to ie and javascript causing 100% cpu usage on certian machines.

my vista machine has problem with the add new user interface,

a win2k machine with ie6 cant even use the compose function without text showing nearly 45 seconds after its typed, and hitting the space bar causes ie to jump to 100% cpu useage.