Optware doesn't work yet on AC builds. In meantime I'm using opkg to install individual packages without any errors. Originally I used /opt but moved to /jffs since then. 
http://www.dd-wrt.com/phpBB2/viewtopic.php?p=776312#776312 
http://www.dd-wrt.com/phpBB2/viewtopic.php?p=777340#777340 

 1. Mount USB under /jffs 
 2. After ipkg update, use ipkg to install opkg 
 ipkg -d /jffs install http://downloads.openwrt.org/attitude_adjustment/12.09/brcm47xx/generic/packages/opkg_618-3_brcm47xx.ipk 
 3. Modify root in /jffs/etc/opkg.conf 

 Code: 
src/gz attitude_adjustment http://downloads.openwrt.org/attitude_adjustment/12.09/brcm47xx/generic/packages 
 dest root /jffs 
 dest ram /tmp 
 lists_dir ext /var/opkg-lists 
 option overlay_root /overlay 

 4. Update opkg 
 opkg -f /jffs/etc/opkg.conf update 
 5. Install missing libc 

 Code: 
opkg -f /jffs/etc/opkg.conf install http://downloads.openwrt.org/attitude_adjustment/12.09/brcm47xx/generic/packages/libc_0.9.33.2-1_brcm47xx.ipk 


 Install any package you like error free 
opkg -f /jffs/etc/opkg.conf install nano