The version V5 is not listed as a supported model for Windows 7. There have been many problems with your router connecting with Windows 7. If your router is not on the supported list it's very likely that it won't work with Windows 7. The last update for your version was 7/7/09 and shows no support for Windows 7. In fact I would have to mark this as solved because your router is no doubt the problem.
You should either purchase a new router or wait for Linksys to come out with firmware update for your model. In fact this same type of problem was just solved by purchasing a new router. Read here> New Laptop can't connect to WRT54GS
The new Windows 7 has attracted many users worldwide. An increasing number of users have switched from Vista and XP to Windows 7.
If you have recently switched to Windows 7 but you are not sure if your devices are compatible with Windows 7, here is the initial list of compatible devices when they launched the Windows 7.
Select one of the following categories to see the compatibility list.
- WRT54G2 v1.5
- WRT120N v1
- WRT160N v3
- WRT310N v1
- WRT310N v2
- WRT320N v1
- WRT400N v1
- WRT610N v2