Wow, no body replied to you...

I had this problem and i used this solution:

my maintenance plan created a job with this step:

EXECUTE master.dbo.xp_sqlmaint N'-PlanID blablabla -To "a.siroos" -Rpt "F:\DailyMajorDbs0.txt" -DelTxtRpt 1WEEKS -WriteHistory -RebldIdx 10 -RmUnusedSpace 50 10 '

Then I add another attribute(-SupportComputedColumn) like this:

EXECUTE master.dbo.xp_sqlmaint N'-PlanID blablabla -To "a.siroos" -Rpt "F:\DailyMajorDbs0.txt" -DelTxtRpt 1WEEKS -WriteHistory -RebldIdx 10 -RmUnusedSpace 50 10 -SupportComputedColumn'

This will work:D

*note: if you open your maintenance plan and save it after changing the step , it will reset the code , so error Will occur again.

So steps are :

1- create and manage your maintenance plan

2- change the steps

2-1 - add the attribute :-SupportComputedColumn

3- do not change your maintenance plan , or if changed redo 2 and 2-1

Thanks,

Ashkan