Yes, there is an issue in MultiSeries's handling of LambertW. It becomes evident by comparing the result of the problematic call MultiSeries:-series( (G(1-h^2) + 1)/h, h, 1) and the result of MultiSeries:-series( (G(1-h^2) + 1)/h, h, 2) (the latter is correct).
Note that all MultiSeries:-limit needs is the first term (dominant term) of the series, so it uses a call similar to the problematic calling sequence above, leading to precisely the same problem.
Please note that MultiSeries:-series(f(x), x=0) returns a series that is valid on a real open interval (0, a) for some a > 0. In other words, a series that's valid as x approaches 0 along the positive real axis. The call MultiSeries:-series(f(z), z=z0) for any nonzero complex z0 returns a series that is valid as z approaches z0 along a ray emanating from the origin. This pathwise semantics makes MultiSeries quite useful in avoiding branch cut issues. The example Robert gave is an illustration of this. To obtain a series that is valid along some other path, one simply performs a change of variables as follows:
> dir := -1: #some nonzero complex number, interpreted as a direction vector
> MultiSeries:-series( G( 1 - (dir*h)^2 ), h=0 );
The above call will compute the series as h -> 0+. I've put together a worksheet that visually demonstrates the series approximations to G( 1 - h^2 ) along eight different directions as computed by MultiSeries:-series. It's available here:
View 5819_multiseries.mw on MapleNet or Download 5819_multiseries.mw
View file details
EDIT: I made a mistake in one of the comments in the worksheet. Each finite limit is really just the absolute value of the coefficient of h^3, rather than one-sixth of it. (It is one-sixth of the absolute value of the one-sided third derivative of H(h*dir)).
For more information on this pathwise semantics of MultiSeries, please refer to its help page.
Finally, the limit computation of a 0/0 expression in Maple should not be significantly different from the limit computation of anything else, since the core algorithm in Maple (both in :-limit and MultiSeries:-limit) is based on some form of asymptotic series expansion with machinery in place to detect indefinite cancellation. To find a 0/0 limit, Maple basically divides the series for the numerator by the series for the denominator, and looks at the dominant term of the quotient series. Problems found in 0/0 limit computations most likely indicate that the coefficients were not computed correctly, as in this example.
Math Group, Maplesoft