Only 1 mac can connect with TimeCapsule

Question

Hi everybody,
I'm havin' a rather irritating problem with my timecapsule ...
I have a MacBook Pro and an new iMac... I set u a network with the timecapsule and normally the 2 mac's can connect on the internet trough the Timecapsule ... Now something changed and when i connect with my macbook, my imac get's trown of the network and loses his connection .. it's like my macbook is prior and gets al the speed... when i try to connect with iMac, i have connectivity for about 5 sec and then the connectivity drops ... Very strange ..
What can be the cause of this ?
Thanx

Answer 1

Disco,
*_Can Only Connect to Network With One Mac at a Time_*
Forgive the size of this post, but the following suggestions have worked for others experiencing connectivity issues like yours. Consider each topic separately. if one does not resolve your issue, then move on the next one.
*Multicast Rate / Transmit Power*
Launch Airport Utility.
Select your Time Capsule on the left.
Click "Manual Setup".
Select "Airport" from the toolbar at the top.
Click the "Wireless" tab.
Click the "Wireless Options..." button.
Check the setting for "Multicast Rate".
This setting controls the range at which you allow devices to access your network. Lower is better if you want access throughout the house. But this setting won't improve speed. Tesserax has a nice explanation of this setting in the following quote:
+"The Multicast Rate option sets the threshold throughput level a wireless client must obtain in order to be "accepted" by the base station. The lower this value, theoretically, the greater number of clients that can connect, especially those at greater distances from the base station. At the opposite end, the higher this number, only those wireless clients that can achieve the higher throughput value will be able to connect.+ [http://discussions.apple.com/thread.jspa?messageID=6736587]
Next, verify that your "Transmit Power: is set to 100%.
*Interference Robustness / Use Wide Channels*
Finally, ensure that "Interference Robustness" is checked (For certain network configurations this setting will say "Use Wide Channels. Verify that it is checked nonetheless.)
Help Doc states: +"You may experience network performance problems if a microwave oven or other source of interference is used frequently near your base station or Time Capsule. To help minimize interference, turn on interference robustness."+
Click “Done”.
Click “Update” in the lower right.
Wait for the Airport device to restart (about 60 seconds).
Then close Airport Utility.
*Adjust Firewall Settings* #
Go to System Preferences --> Security.
Click the Firewall tab.
Change setting to “Set access for specific services and applications”.
The System will now ask you when each process wants to penetrate the firewall. Once you click “Allow” each time you are asked, it will be saved in the pane at the bottom of this window and it should never ask you again.
One poster observed, “Since I made this change, my wireless has been strong and Time Machine works like a champ and the impact on my network performance is minimal. I speculate that the change in performance is due to security protocols or services that run in the 'allow all incoming connections' and 'allow only essential services' modes. Whatever the reason this fix has worked for me for over 2 months without resetting my airport connection or time capsule.” [http://discussions.apple.com/thread.jspa?messageID=8348496#8348496]
*Wireless Security Issue*
Launch Airport Utility.
Select the TC on the left.
Click "Manual Setup".
Click the "Wireless" tab.
Now for "Wireless Security" select "None".
Click "Update".
Now try accessing the internet with all each of your Macs. Does the problem still exist? If not then you may need to clear out your previous security settings.
First, change "Wireless Security" back on using "WPA2 Personal".
Create a new password in the 2 fields below.
Uncheck and recheck "Remember this password in my keychain".
Click "Update".
Next, on each of the 3 Macs add the new password in the Network Preferences and click "Apply".
Finally, try accessing the internet with a 3 Macs again.
If this doesn't work, then we may need to go into Keychain and remove any old references to your Airport network.
*Reset Time Capsule Password on Affected Mac*
Try the following. Read and follow the steps very carefully. You may find it helpful to print this post first as you will lose network connectivity for a short time.
On the Mac that is experiencing the network issues launch Keychain Access.
Select "login" from the Keychains pane in the top left.
Highlight "...Passwords" in the Category pane from the lower left.
Sort all the items by “Kind”.
Note everything labeled "Airport...". How many do you have listed? There should only be one "Airport base station password" for each base station that you have active, and there should only be one "Airport network password" for each network you have created.
Delete the “Airport network password” entry for the network in question.
Close Keychain Access.
Now go to System Preferences.
Select “Network” Preferences.
Highlight “AirPort” in the services pane on the left.
Click “Advanced…”.
Click the “Airport” tab.
Highlight the network in question.
Delete the network using the tiny “-” button.
Verify that “Remember any network this computer has joined” is checked.
Click “OK”.
Click “Apply”.
Click “Turn Airport Off”. Wait 10 seconds.
Click “Turn Airport On”.
In the “Network Name” menu select the network in question.
Enter the network password.
Check “Remember this network”.
Click “OK”.
Click “Apply”.
Reboot your computer.
After login you may be presented with a window stating “None of your preferred networks are available”.
Select your network.
Ensure that “Remember this network” is checked.
If you wish, you can check “Show password” for verification.
Click “Join”.
If you go back into Network Prefs and click “Advanced…” your network should have returned to the “Preferred Networks” list. Drag it to the top of the list so it has precedence. If you have done so, click “OK” and then click “Apply”.
Now see if network connectivity has improved for the affected Mac. Let us know if the above was helpful.
Cheers!