Some convection ovens have the ability to turn off the fan -- if yours has one, that would be recommended.
One of the big issues is that the cooking time changes based on the surface area of the item being cooked -- so if you have a thin cake, such as a jelly roll (baked thin, then rolled up), your cooking time will be dramatically reduced ... but it doesn't help with large cakes -- you'll just end up with the top browing faster than the middle sets.
In general, the recommendation for convection ovens is to lower the temperature by about 25F / 15C (some newer ones with digital controls will do this automatically), but some people report problems with cakes being overly dense; I've heard different theories (eg, bernoulli effect lowering the pressure in the oven, causing the air bubbles to come out of the batter). Adding a tight covering of aluminium foil might help this, but it will cause other issues (eg, steaming the top).
Another recommendation I've seen for baking in a convection oven is to make sure that your oven has had sufficient time to pre-heat, then when putting in your baked goods, turn the oven off, and leave if off for 3-5 minutes before turning it back on. (this is typically to solve problems with baked goods appearing lopsided, as the fan's blowing so hard it's moving the batter around significantly).