I was having very similar issues with Tomato v23. Never had any issues with v19 and wish I had never upgraded. Switched to DD-WRT and the problems went away. Shortly after, I decided to upgrade my network to gigabit throughout so my Linksys router gave way to a new DLink DIR-655. Took a while to find out what all the setting did, but now everything is running perfectly. I still have DD-WRT running on my WRT54GS which is now a repeater for my DLink.