Kontact and kmail 4.3.1 extremely sloooow


for several days I tried to figure this out by myself, but I can’t. I’m about to change to Thunderbird, but it won’t be possible anyway.
What happens:
Whenever I start kontact, as soon as I hit one mail in order to view it, it slows down dramatically to the extent, that it is impossible to work with it.
It takes a few seconds until the contents of that mail becomes visible. Then clicking on the next mail, it just sits there, doing nothing for half a minute or more.Eventually, it will highlight that message, but the contents isn’t shown for another minute or more.
I have tried removing the kontactrc, but that didn’t change a thing. I also tried removing the kmailrc (which I usually wouldn’t want to do, as the amount of individual settings in there is tremendous), no change.
The Sysguard shows activity in kontact,up to a certain level, when several kio_pop3 (in total five) and kio_file (in total three) processes are opened (filtered by “kontact”). Then, the activity stops (no cpu usage, no increase in RAM usage, which remains at a relatively low level), and I can’t access Kontact any more. It just gives me a grey screen.
I use OpenSuse 11.1 64-bit and KDE 4.3.1, my machine has 8 GB of RAM and an Athlon 64 X2 5200+.

Any idea what I could do? I use KMail heavily, and people rely on my quick responses.

Ok, the days of searching for the cause of the problems are over. After checkling the processes itensively, I figured out that spamassassin was slowing kontact down to the limit.i searched and found an article that says that it is better to run the set of spamd/spamc for the check of emails. My current installation provides of course the two, so I changed the filter settings (it still took a long time to do that) where all messages are run through spamassassin, and from then on everything is fine again.

Strikes me, though, why it started being so resource hungry (one process took about 40 to 50% of CPU power) just recently, and why it suddenly had such an effect on kontact. After all, I had mails run through spamassassin for a long time with no such effect.