I had a similar problem to this on a MX6000 and it too was caused by a dry joint. Out of the 11 MX5500/MX6000/MX7000 TVs I have repaired in the last 3 months only 4 had real component faults. The rest were dry joints. Whilst I had the sets in pieces though I often change the PSU capacitors, the elcos around the frame/line circuits and some of the elcos on the tuner board. You could visibly see the difference in the picture after changing them. See this very informative thread for details
http://forum.beoworld.org/forums/thread/78908.aspx
Some of my B&O: BV3/32, MX7000, MX5500, LX5500, MX4000, BM8000, BM6000, Overture, BL8000, BM6000 Quad, BM4400, BM3400, BG-CDX, BM3000, BM1001, BM1200, BM1600, BM1700, BM1500, BM1400, BM2400, BM2300, BM4500, BM4000, BVM70, BVS45-2, BVS60, BC7700, BM2200, BM1900, BG8002, BM1202, BVPenta, BVP45