I do experience the same problem, from time to time to time dragging an attachment from nautlus will produce the described symptoms. IMO this doesn't have anything to do with the size of the file, though - try using the "send to" dialog in nautilus - this way evolutions ends up eating all the resources in 100% of cases, even with files (odt) as small as 33 Kb, at least this is how it look on my machine (macbook pro 5,5, Karmic Beta).
I do experience the same problem, from time to time to time dragging an attachment from nautlus will produce the described symptoms. IMO this doesn't have anything to do with the size of the file, though - try using the "send to" dialog in nautilus - this way evolutions ends up eating all the resources in 100% of cases, even with files (odt) as small as 33 Kb, at least this is how it look on my machine (macbook pro 5,5, Karmic Beta).