Time Capsule with very slow network throughput

Question

I have a TC that is only supply about 5% of the network throughput it should do.
We ahve a 2MB connection and any computer that is connecting to the TC wirelessly is only getting around 0.1MB. The signal is strong, the noise is low, it's on an isolated channel (no other networks overlapping). It does this regardless of whether I switch to wireless-g or wireless-n (2.4GHz or 5GHz) and regardless of which channel I select.
I plugged in a different TC and I got my 2MB connection no problem.
So I think the first TC is knackered. Luckily it's still under the 90 warrantee. I want to return it to get a replacement, but I can't get through to the apple care telephone service. I've been on hold for 20 mins then got cut off without talking to anyone - this happens every time I call. Why on earth anyone would pay for apple care is beyond me if you can't even get through to Apple!
Can you just take a TC back to an Apple Store and get a straightforward replacement?

Answer 1

Sorted it! I hit the factory reset button on the back and started again from scratch.
There must have been some software issue in the TC itself that could not be addressed through the configuration interface.
I hope this helps anyone who has a similar problem. In summary this is what I was experiencing:
1. When connected Mac Mini to TC with ethernet cable I had top speed access - so no drive writing issues.
2. Set up the TC to share our 2Mb internet connection as a wireless-g network. When connected a laptop to TC via the TC's wireless-g network I had excellent signal strength, low noise, and an uncluttered channel (as indicated by iStumbler) - so no interference issues with other netowrks, microwaves, cordless phones etc.
3. The laptop reported an excellent signal strength and potential rate of 54Mb.
4. Used an online broadband speed tester (www.cnet.co.uk/misc/speedtest) on the laptop to determine the actual throughput. The result was around 0.2Mb. Not good.
5. Tried copying a file from the TC over to the laptop and monitored the throughput using the laptop's performance monitor. The result was still around 0.2MB.
6. Tried changing the wireless-g channel. Same result.
7. Repeated the above with a wireless-n network. Same result.
8. Finally, hit the factory reset and repeated points 2 - 4 above. Got almost 2Mb, which is what I was after!
Hope this helps someone.