Question... am I liable for UK tax

I worked full time and was taxed in the UK up until July 2005

At this point I moved to Qatar (where there is no income tax). I was paid from the US whilst working there and paid no tax anywhere, claiming residency in Qatar.

I have now moved to the US (as off 9th April 2007) on a J-1 visa to work here for a set 18 month period. I have a certificate of exemption from US tax. Whilst working here I will be paid from the UK and my employer is telling me I have to start paying UK income tax.

Am I not still non-resident as I was whilst working in Qatar? I came here straight from being a Qatari resident, so does my residency still lie there?

If anyone can help I'd be really greatful:confused:

Sorry, yours is a UK tax question, an area on which I have NO expertise.