Only last week we had a poster who's wheel alignment issues were caused by a misaligned subframe. Either its been bashed at some stage or if its been moved to replace the anti roll bar it might not have gone back correctly. Only needs to be a tiny bit out to give wierd problems. Can't find the other post right now but i don't think its a huge problem to fix (as long as its not bent!!)
It would have to bashed pretty hard to move it so either it has been removed and refitted in the past (ARB or steering rack change) or it is bent.
Lower bushes would be the more likely issue though, and I have also seen lower wishbones that are aftermarket and with poorly fitted bushes which throw out the lower arm by a mile - so even if the bush isn't knackered, the arm might be out.
Incidentally, the subframe is located in place using locator pins (don't know the correct name) whilst it is bolted up. If someone has not used the locator pins and done it by eye then it could be a few mm out which translates to about a meter out when it gets to the edge of the wheel! (or at least it feels like it).