This limit is caused by the configuration that DreamHost use for their PHP installation. This limit can not be raised as you do not have access to the php.ini file.
However, you can compile/install a custom PHP installation and modify its php.ini to raise the limit to whatever you want. Details are in the wiki article linked below.
Save [color=#CC0000]$50[/color] on DreamHost hosting using promo code [color=#CC0000]SAVEMONEY[/color] ( Click for promo code details )