OK, not much more I can add over a public website.
If your land is not currently registered at LR there is a definite problem - it should have been. It doesn't take months to do this - it is perfectly straightforward. When you bought the land, this should have happened. It is tied up with the payment of Stamp Duty Land Tax - see here: -
http://www.direct.gov.uk/en/MoneyTaxAndBenefit s/Taxes/TaxOnPropertyAndRentalIncome/DG_401591 8
Did you pay your solicitor that money for him to do this job?
Whether that NOW entitles your new buyer to now pull out if you did exchange contracts, I'm not sure. Whether you have actually exchanged contracts already before this was realised, again I am not sure.
Either way, these are not things the average man in the street expects to worry about - that is what one pays a solicitor for. In terms of getting something positive out of this for you, it will probably help if you happen to have used the same solicitor for the purchase in April 2007 as for the sale now (its just one organisation to point the finger at). I suggest that you go to CAB for a bit more free advice - they may be able to put you onto a solicitor where you can get 30 minutes of free advice to help you get to the bottom of this. BM