Tier 1 General Migrant - Change of circumstances

I'm venezuelan and I hold a tier 1 (General) Migrant permit. Since June 2010 I moved to Germany and now i hold as well a residence permit for germany because my husband is german. During the summer 2011 I was working with my ex-boss in a project in London and I was commuting every week between the uk and Germany for 3 months. I never had any problem. Since December I started again another project here in the uk, same circumstances, I'm traveling every week back and forward.
Last Monday the immigration officer told me that I can't use my tier 1 because my circumstances change. She said that I need a business visitor visa, because my tier 1 was approved for me to live and work in the Uk.
My point is, with a tier 1 visa could I live between both countries? There is something in the law that Prevent me from doing it?
She said that she will allow me in Because I didn't know it was illegal and I did have a return ticket in 4 days. The problem is that I'm suppose to come back on Monday and I'm not really sure what to do. Does anyone have any similar experience?