according to o2 coverage http://www.o2.co.uk/coveragechecker the 2g coverage is near as 100% of the isle of wight indoors and outdoors although you have to appreciate dead spots will always exist particularly indoors. 2100 mnhz 3g is poor, basically covering a small part of the the north of the island but 900mhz 3g (3G900) is or should be pretty decent covering the majority of the island.
is your phone switched to 3g only as that would explain your signal issue particularly if your handset isnt 3G900 compatible? I always try switching to 2g only mode if the 3g signal is poor as i generally find the threshold that my mobile hangs onto 3g isnt particularly high although the calls do tend to handover from 3g to 2g fairly reliably.....sorry mate if i am teaching you to suck eggs!!!
if the above isnt the cause of the problem it suggests some kind of network fault or upgrade was in progess, although i had a quick look and couldnt find anything. (it was only a quick scan though)
oh and alyamani the poster is asking about the isle of wight (covered by 02UK) not the isle of man which is classed as roaming.
Hey I lived on the Isle of Wight till fairly recently and I can say that coverage is rather patchy regardless of what coverage sites say! If you go to the south west coast you can sometimes find yourself 'roaming' on a french network
But hey it's the Isle of Wight, behind the times and we like it that way!