Multiple bands in eluted PCR product - (May/02/2012 )

hi all,
I have done PCR using a universal primer and eluted the PCR product from the agarose gel using Nucleospin kit. Eluted pcr product on agarose gels is showing multiple bands on gel electrophoresis.
the PCR product of mine only showed single band but after elution am getting multiple bands...why am getting this multiple bands after elution?
I have repeated this elution using QIAGEN kit, i have also tried with different primers, and also modified the elution kit method (cooled the sample to reanneal after incubating at 50ºc for melting the gel) ...but still am getting multiple bands after elution. from the multiple bands of eluted product i have also cut the desired band and eluted that,but still i got multiple bands.. please give me a suggestion to solve my problem....
thank you in advance..
-anna.

Could your elution buffer be contaminated with DNA? Perhaps you don't see the second band if the sample is not concentrated.