Q: iMac wireless connection probem

Is this something that worked before, and is no longer working for some reason?  Or is this the first time you are connecting this iMac to that router?

This is a PowerPC iMac (G3, G4, or G5) running Mac OS X Tiger (10.4.11)?  Does it use an Apple AirPort card (internal) for wireless, or are you using a third-party adapter of some type?

Mac OS X (10.4)

Use Software Update to update your OS to last version of Tiger.  Install all the other updates that goes along w/it.

Change your router channel number.  Most times this works & is all you have to do.

System Preferences>Network

Click the Assist Me button.

In the next window that pops up, click the Diagnostic button & do the necessary.

See KB Articles:  http://support.apple.com/kb/HT1401 AirPort troubleshooting guide

http://support.apple.com/kb/HT2712 Using network locations in Mac OS X

Manually provided DNS server addresses are higher priority than DHCP's

http://support.apple.com/kb/HT1714 Solutions for connecting to the Internet, setting up a small network, and troubleshooting

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Also, run the Airport Utility app which is located inside the Utilities folder.

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If using a  Linksys router, contact LinkSys Customer Support and/or post in their forums.

If using Apple's Airport, please re-post over in one of the AirPort Forums.