I just updated mine with the V4 (as I have the hard case unit) and it worked fine. It took about 2 minutes. In the past I've never been able to update, and now I realise it's because there are 2 hardware variants of the ice>Link Plus, and I obviously have the later one. All past firmware updates that have been posted here are for the old hardware.
All Dension have done is change what number 6 does; it now toggles between iPod control and stereo control. There are no settings available now, such as charging, which is a bit annoying, but at least it works properly now. JCW Sound Kit | H/K | Sat Nav | SS+ | Xenons | 17" Anthracite R90s | Goodyear Eagle F1 GS-D3s | ... |