ETS amplification problem

Hi all,
I've been having problems amplifying ETS from plant samples. I've been getting a band in my negatives and this band has been around in my lab for some time now. Some people have sequenced it without getting any results (i.e. nothing, being a dye blob or something) but then i sequenced it and I got a full 400bp sequence!
Now everybody is freaking out and we can't get rid off it. I've tried UVing the stock primer, change set of primers (ETS B - 18sIGS to ETS B - 18sE) reduce amount of primer in master mix to half, amplifying without BSA, and changing annealing temperature. I was wondering if anyone has had this problem too.
Thanks a lot

Simon