in Vuze 5.5 I noticed a strange trade-off between upload and download speed. As soon as the upload speed increases, the download speed decreases considerably. That didn't occur in Vuze 5.4 and seems inexplicable, since I have an ADSL with static upstream and downstream bands, speed limits are trimmed for the available bandwidth and no other applications are sending or receiving data. Do you know of any issue or settings in Vuze 5.5 that could cause that?
It looks like it was only a router issue. For some reason the router had negotiated a lower rate than usual, which affected the overall throughput. After a reboot and resync everything seems ok.
However, it is unclear why download and upload speeds were affected even if Vuze speed limits were set quite lower than the upstream and downstream rates reported by the router interface, but that could just be caused by a firmware problem of the router.