Question on wired PCR - (Jan/12/2010 )

Dear all,
I am here to ask a strange PCR result? I do one multi-plex PCR with bioline enzyme. I use 94 degree to denature the DNA. The results I got is very strange. I always can see a big smear smear from the DNA loading well to DNA ladder 2 kb position. I don't how this things happens.
Maybe some one you here can give me some adivce to give ride of it. I have used the same template to do another PCR and the results are very specific.
Thanks you all in advance and happy new year.
Attached you can see how the picture looks like.

Do you experience such incident when individual primer pairs from the multiplex were used?