Bands are like a "w" - (Aug/06/2004 )
My box-PCR (bands range about 2000bp to 350bp) have shown bands like a "w". My agarose gel is 1,5% and I run it at 50mA and I use TBE.
normally strange band shape is to do with the gel, for example agarose not dissolving properly before you por so there are clumps, or setting slightly before you pour- again causing small clumps that would cause the sample to run unevenly. Try decreasing the agarose conc and make sure it all dissolves properly. It could theoretically be a problem with your power supply, but then you'd get a strange pattern all over your gel, not the same for all bands.