Restart the TC.. it is buggy..
You will need to do this occasionally.
Is it working in bridge or main router in the network?
It will help if you do a few things.
Use SMB names.. short no spaces, pure alphanumeric.
Use WPA2 Personal security.
Use fixed radio channels.. change it to manual and change the 2.4ghz to 11, 6, or 1.. try them in that order.. stick with what works the best.
There are a few other things that might help but cannot totally fix it.
Unfortunately the latest TC cannot revert firmware to a version that matches your 10.6.8 computer.. but it will match Lion or Mountain Lion which is probably on the air.
By restart, I assumed you meant, "unplug and replug". Did that. No difference.
It is the main router.
So I reaccessed the TimeCapsule through my wife's Mtn Lion computer, changed the name of the Base Station (removed a space), and then changed the radio channel to "11".
Once everything restarted, I was able to access again via my MacBook 10.6.8.
So, for the time being, all is well!