Actually, FordPrefect, it isn't the fact that it's less than 2 that causes the problem.
Consider base sqrt(5), which is greater than 2. (sqrt(5) ~ 2.236). Take decimal 280, which is 2010100sqrt(5). But the usual conversion routines will give 10000000.1001...sqrt(5), since sqrt(5)7 is 279.51, which is closer to 280 than 2*sqrt(5)6, or 250.
Same for base sqrt(10), which in some ways is easier to work in, and is greater than 3. 322 decimal is "obviously" 30202sqrt(10), but it's also 100012.12...sqrt(10), by similar reasonings.
I'm thinking it may also have to do with the way the base0 place works. Ponder: the equations 10-1=(b-1) (where b-1 is the digit for one less than the base b) works for all integer bases, but does not work for irrational bases. The problem is that we're using integer multiples of integer powers of the base, and when the base isn't an integer that isn't so well-behaved anymore.