Router problems

A bit more information could help:
- What router?
- Wireless setup (encryption, etc.)
- What laptops? (most important: which WiFi card?)
- Which operating system?
- What app do you use to test?
- Do pings work?
- Does pinging inside the internal network work?

Jam it back in, in the dark.

Then try pinging the other systems in the internal network. In both ways (meaning if machine A is the problematic one and B and C work: try pinging B and C from A and also try pinging A from B/C).

More stuff to try:
- Check event log on system A for suspicious messages about the network
- Is there some sort of log on the router? If yes, then check it
- Try resetting the router settings (backup everything important prior to do that), sometimes rebooting doesn't do the trick
- Try disabling WPA2 and test connection with unencrypted setup

There's nowhere I can't reach.