I have a Gateway laptop, with Windows Vista SP2, and a Linksys-Cisco WRT54GL Wireless-G Broadband Router. When I boot up my laptop, it automatically connects itself to my home network. Then at random times, it disconnects itself from said network. I go to reconnect it, but I get an unknown error and none of Vista's suggestions are working. Sometimes, after 5-10 minutes, it will reconnect itself. I've already tried updating the firmware. I can't install any other firmware, or make a factory reset. My dad owns the router and buys the internet and he won't let me TOUCH it. I can't do ANYTHING to it.
Before you go messing with the firmware, have you tried to check for simple things that might be causing the problem. I once had a cheap baby monitor that kept kicking my laptop off the wireless network. Often times a cordless phone can also have this affect since the phone and the router both operate at 2.4GHz. If those aren't the problem, then a possible firmware update might be in line. However, if I was going to use an aftermarket firmware, I would definitely use DD-WRT instead of Tomato.
Another possibility, especially if the issues occur after your computer has been in sleep/standby, is to disable power management for your network card.
Right-click 'My computer' -> Device Manager -> Double-click your network adapter -> Power Management -> Remove tick in "Allow the computer to turn off this device to save power".
This helped me on some networks, where I could see the network and have excellent signal strength, but it would not connect.
I had this problem on a Vista labtop with a Linksys router. After several months with no solutions, I tried Tomato. It fixed the problem, and I never looked back.
DD-WRT is an excellent solution. When Fonera was giving away free acess points, I grabbed two access points and went to work. I love the front and back end of the software.
One thing I would suggest taking into consideration is faulty hardware. Check to see if all other devices remain connected and ensure that the router itself does not constantly reboot.
Another thing to take into consideration would be if your ISP utilize DOCSIS. If that is the case, your router could be being forced to upgrade/downgrade its firmware and is stuck in a loop.