Two things which might help
1) Switch of 'Wireless N' in any router you control.
2) Update the wireless ROM if you are able and willing to hack your phone or else take it to the retailer and insist that this is done for you.
Wireless ROM images are here
[GSM] 24/11 - Hero ROMs + radios in update.zip format - Android @ MoDaCo
the latest is the topmost 63.18.55.06JU_6.35.08.29