top -I and load average from 4.9 into 5.4

[pobox at verysmall.org]

We upgraded from 4.9 to 5.4 and the 'top -I' and load average seem to 
behave slightly different. 'top -I' in 5.4 stays empty most of the time 
with processes flashing in and out from time to time. In 4.9 the 
processes stayed there until they are done. Load average on another hand 
does not seem to correspond to the CPU load seen in 'top' (as 'top -I' 
is kind of useless at the moment) - i.e. load average can be 1 and in 
the same time the sum of the CPU usage in 'top' is around 50%.

Can anyone suggest why these behave that way?

Iv