AV updates and how there done are VERY time, and resource intensive.
Unfortunately there nothing much ZA 9.3 can do about it because its just how Kaspersky's AV update engine works and we cant fix there code.
Many many times AV updates will bring a system to a grinding halt so you cant do anything until it has finished.
I seen this on XP SP3 system and Win 7 systems, with slow and fast performing systems.
Some systems with a P4 and 1 meg of memory perform better than a quad core Win 7 system and visa-versa. So even that latest technology can have this issue sometimes.
But the MAJORITY of ZA users don't have these issues. Its not wide spread over all AV users.
The next Major release of ZA 10 (Released June 7,2011) will incorporate a brand new Kaspersky engine and new AV update system that will improve performance some.
Its not going to fix everyone since each persons perception of what is fast and acceptable is different.
So hang in there, AV update performance improvements are coming.