[imp] weird informations showing in the message head

[Woerns Urstmann]

when i have a mail with an attachment, the attachment is displayed corectly in 
the end of the mail. but right under "header" i have an additional line "  1  
unnamed  text/plain  0,33 KB" when i click on it i can download a text file 
containing the mail (that is already correctly displayed in imp)
how can i get rid of that line? it's confusing my users...
thanks
jens