Game "running out of memory" with 32-bit JRE's

My game is more on the graphically demanding side; It loads a lot of high resolution diffuse textures, normalmaps, specularmaps, and glossmaps. On 64-bit JRE’s this is no problem. But I cant seem to allocate enough ram to get the game to boot with 32-bit ones.

This is my command line:
java -Xmx1024M -Xms1024M -jar client.jar