Using the latest release 3.3 of GAP, the following weird phenomeneon
occurs:

gap> IsSolvable(Group((1,8,3,6),(1,2,3,4),(5,6,7,8)));
true
gap> # Now, switching the first two generators, yields:
gap> IsSolvable(Group((1,2,3,4),(1,8,3,6),(5,6,7,8)));
Error, RemoveSet: <set> must be a proper set at
RemoveSet( T, v ) ... in
ExtendElementaryAbelianSeriesPermGroup( G, w, der - 1 ) called from
ExtendElementaryAbelianSeriesPermGroup( G, w, der - 1 ) called from
ExtendElementaryAbelianSeriesPermGroup( G, y, bound ) called from
PermGroupOps.TryElementaryAbelianSeries( G ) called from
G.operations.IsSolvable( G ) called from
...
brk> quit;
gap> quit;

Peter