Probably you got too much salt in your DNA after the qiagen gel kit. Use PE washed twice and in each PE wash, after you add PE, let it stay for 2 -3 min before you spin.
It may be due to the remaining agarose and its residues in the elution. Try Qiagen PCR Purification Kit to purify your products. It may solve your problem.
【在 H*g 的大作中提到】 : It may be due to the remaining agarose and its residues in the elution. Try : Qiagen PCR Purification Kit to purify your products. It may solve your : problem. : : Gel