What nappy cream have you been using? If you use a zinc based cream it can damage your nappies as I understand... so things like metanium etc.
Ladies can you use disposable liners with metanium or zinc based creams? I never have - I've found calendula from Weleda really good. We have had a few occasions (fortunatley not many) when LO was teething that we had to use disposables because he needed metanium.
Interesting because we also had issues with nappies that weren't absorbing... then at baby show I spoke the woman from Bum Genius about the fact our tots bots were no longer... she suggested I was overboosting and suggested strip washing... haven't looked back it's been amazing!
The advice was any boosters etc that didn't have a waterproof PUL lining could be washed with a dishwasher tablet as this would strip all the powder out of the nappies. Unfortunatley the easy fits like most all in ones couldn't be washed in this load... so I just washed them a few times with no powder. She said wash, rinse, wash, rinse etc until you can't smell anything (it just takes a few more washes than if you use the dishwasher tablet). Apparently if nappies smell nice and fresh they have too much powder, if they smell of amonia (as mine were starting too) you have had the problem for a while and the wee smell is sticking to the powder in the nappies.
Nowdays I tend to do a rinse cylce with powder and then a mini 40 wash with no powder. My nappies rarely come out with any smell but once every 3 months I do a full strip wash of every booster, or nappy inner that I can. I then also take advantage of a less environment moment and fluff them up with the tumble drier.
The tot's bots (I have easy fits) just get an extra powder free wash every now and then.
Hope that's helpful... just don't use the dishwasher tablet with anything that has a waterproof layer as they have bleach which damages the waterproof layer and would leave your nappies useless! Apparently the newer bum genius nappies have a waterproof layer that withstands this... but I can't see why you would need to strip wash the waterproof layer (unless it's part of an all in one perhaps).
Good luck! Let me know if your nappies come out any better.