What I can't do, is write with my hands. I've never been able to (I'm in my 40's now). It's like I don't have fine motor control over my fingers to form letters, even though I can build and make tiny things with my hands and fingers. I have to grip the pen or pencil with a vice-like grip just to be able to move it in small movements.
Additionally, letters get written in the wrong order or back to front. The frequency of this happening is every other word or so. Even short words like 'and' or 'to' can get screwed up.
To combat the problem I switched to all-caps in my handwriting during secondary (high) school. To this day I avoid writing anything by hand if I can help it. I've never been able to actually pin down whats wrong with me, so the best I settle on, 'is some kind of dyslexia'.
I'm also left handed, but I'm not sure that's a factor.
EDIT: Thanks guys! It's definitely 'dyslexic dysgraphia' as per the Wikipedia article. Like RobertRoberts said in a comment below, this is why I frequent HN more than any other forum. You won't believe how much better I suddenly feel about this.