I think I've found something that may be the cause! Reading Robin Walkers page about Channel ID's and Upstream signal levels, I checked the settings on my Surfboard 4100.
Channel ID was set at
4
Power level was
+58 dBmV
So I changed the channel ID to 1 as his page suggested certain channels could be overloaded. I saved the changes in the modem and rebooted it. Disabled Zone Alarm and Adsubtract for testing, and was able to upload a 1 meg file to my Briefcase! However, I can't do it again now? So I tried a smaller file, 433kb, that uploaded OK. Tried it a second time and it wouldn't work, a third time no go but the fourth time it worked, so it's still hit and miss! I enabled Zone Alarm and tried the 2 files again and found it was still hit and miss, sometimes the file uploaded, but more often it didn't.
Further reading on Robin Walkers page found this interesting quote:
Quote:
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The upstream transmit power will lie within the range +8 to +58 dBmV, with many ISPs specifying a target commissioning level below +55 dBmV. Values in the forties are the most common. Many cable modems are unable to transmit any more powerfully than +58 dBmV. One cannot tell how far this is below the figure that the UBR would need to see a strong enough signal at its end to maintain satisfactory performance, so a figure as high as +58 dBmV is normally a sign of an unacceptable return path. If other problem symptoms are also present, an upstream transmit power of +58 dBmV would constitute valid supporting evidence for requesting technical support from a cable ISP.
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Note the bit i've highlighted in RED and the 'other problem symptoms', like can't upload files for instance? It maybe coincidence that changing the Channel ID worked as it may be a fluctuating upstream power level that's the problem, letting me upload successfully one time and failing the next time! So that could be the problem, the upstream power level is too high?
So I rung NTL. Basically they did some tests, no problem as far as they were concerned, changing channel ID wouldn't make a difference and power levels were OK, so goodbye! Was advised to drag me PC to a friends house who has NTL Broadband use his cable modem on my PC to see if the problem is still there, then try my cable modem in place of his and see what that does! This would also prove my Ethernet cable as I'll be using a different one at the friends house, as suggested by the NTL guy.
I feel like joining a circus with how many friggin hoops I've had to jump through to tell them there's a problem!
We'll see what this next step achieves!!