Tamron rear lens problem

[snappingturtle]

Hi,

I was cleaning my newly purchased Tamron lens when I noticed to my horror that there were scratches on the rear lens after I wiped it. This is strange because I used the same lens cloth to clean the the front lens as well as other previous lenses I used and there were no scratches on them. Why would my lens cloth scratch the rear of the Tamron lens but not the front? Anyone know the problem?

Second since I am new to purchasing these photo equipments, anyone know warranty policies? All that came with the kit is a simple survey paper, but I could not find anything that explains terms and conditions of warrenty. Any other solutions to the problem?

Thanks,

Hugh