Some clients offline for 2--3 days and shown the defination is older version but some even didn't shown in the log.
The clients that are showing offline can only display what it was they had when they last reported in. Are you saying some clients have never reported in? You'll need to determine why, if that's the case, on the individual machine.
In the segment you copied, 'Last virus time' shows 8/7/2009 13:41. Where do you see 'Never'?
sandra