Problem with D-Link DSL-G604T?

[#1]

I have a DLink DSL-604T router which sometimes seems to get into a strange mode where it seems very busy (lots of flashing lights on my switch and very slow to log into the admin page). When it's like this the broadband response is dismal although the sync speed reports as unchanged. Cycling the power fixes it for a while. It's running the latest software. It's only done this since I moved to a new (old) house which has pretty awful overhead phone lines. Does anyone know if there's a known problem with this router and a different one would work better or is it likely that the poor phone lines are the real problem?

[#2]

I advise you to check you useage and that the router has its wifi secure.

[#3]

Thanks for that. This isn't the problem though. The wireless is of course secured and useage lines up with what I'd expect. The problem seems to be more to do with the router getting into some sort of busy mode and what I had wondered was whether it was known that this model doesn't cope well with poor/noisy phone lines (mine are all overhead and with quite a bit of crosstalk and interference).

[#4]

Is it running hot? I had similar problem when router was pushed up against scanner restricting the right hand vents.

[#5]

AFAIK there are postive reports about this router managing well with noisy or substandard lines.
I often fall out with mine because it reports odd figres for uptime etc, but its always been rock-solid in terms of ADSL performance.
I'm a big fan of Netgears kit, particularly the DG834 in its various guises. I've bought one to replace my G604T with on the basis of dodgy reporting of some things, but the replacement has been sat in its box for the last month or so - the G604T hasn't given me a compelling reason to change yet.
The line the D-Link box sits on delivers great stats, so I can't vouch for its stability on dodgy lines.
I am pretty happy with the kit itself though, although admittedly I have a cynical slant on its future in my setup.

[#6]

I've got a 504T flashed with the 604T Firmware.
Is it all your connections or only the wireless? I find that I need to cycle the Access Point every so often.
The other thing that might be worth looking at is is PlugNPlay turned on it. I've found that with it turned on the router seems to clog up faster and it can become unresponsive to the webadmin front end

[#7]

These are the 604T's DSL stats ATM. They're pretty typical though the downstream rate is more often a bit lower than this. The margins seem quite high - anyone more knowledgeable than me about this?
DSL Status
  Connection Status Connected
  Upstream Rate (Kbps) 448
  Downstream Rate (Kbps) 2176
  US Margin 21
  DS Margin 10
  Modulation MMODE
  LOS Errors 0
  DS Line Attenuation 44
  US Line Attenuation 54
  Path Mode Interleaved

I never seem to get a download speed anywhere near what I'd expect from my sync rate.
Results from the BT Speedtester tonight at about 22:30:
Test1 comprises of Best Effort Test:  -provides background information.
    IP profile for your line is - 1500 kbps
    DSL connection rate: 448 kbps(UP-STREAM)  2176 kbps(DOWN-STREAM)
    Actual IP throughput achieved during the test was - 353 kbps
Overall I think I have a problem of some sort that I can't pin down. It doesn't help that my house doesn't have a master socket (the 2-4 wire stuff is somewhere underneath the floor) so I can't check the wiring at my end very well.
By the way, SteveA - what's the PlugNPlay option? I can't find anything to do with that in the setup.