The exact same problem occurs on my BB Pearl 8100. The radio occasionally turns itself off for a minute of so and then goes back to full reception. I have tried different firmware updates which have been release in the past year (4.5.0.55, 4.5.0.69, 4.5.0.124, 4.5.0.174), but neither one of these four updates fixed the problem. I fear we might just have to live with this issue