problem with FTP - seems limited - please read!

Thanks for taking your time. Let me explain what is going on. It has been 3 or 4 days that I am having problems FTPing. I can connect to the host providers and start the FTP, after a certain size (30k) it stops the transfer.
This is the problem, but now let me explain the possible causes and the tests I have done already.
- I was trying FTP with Dreamweaver, but I had the same problem with CuteFTP - so it is not a software problem
- my internet provider is Road Runner, it can still be the cause or the modem can be broken. But I have no problems to download, only upload.
- my computer, or its os (WIN XP) is not the cause, cause I tried with another computer and OS (Win ME)
- My host provider is not the cause, because I tried with other host providers
- I use a SMS router, but I also tried connecting directly to the cable modem

I talked with the support from road runner. I asked if they had any firewall or were limiting uploads. They said no. But maybe they don't know there is something wrong.
The only test, I guess I can still do, is connection through another provider.

Have you ever seen anything like that ?
I need to upload my websites and I can't in the current situation.

Thanks a lot for helping.

Yan Grossman

Thanks for the interest. I can move files in the network. I also was able to upload connected through another ISP (dial up netzero).
So, eliminated all possibilities, I guess the cause must be road runner or the cable modem itself.
What do you think ?
Thanks