Series command no longer expands arbitrary functions after aborting previous evaluation

Question

I asked Mathematica 9 to execute the SeriesCoefficient command on a rather horrendously complicated expression. After some time I decided to abort the evaluation and try something different.

Somehow, this has caused the Series and SeriesCoefficient commands to stop working properly. They can still correctly expand known functions, for example things like Series[x^2*BesselJ[Sin[x],x],{x,0,5}] do work as expected, but for arbitrary, not-yet-defined functions they no longer work, so Series[f[x],{x,0,2}] now returns just f[x] rather than the expected f[0]+f'[0]x+f''[0]x^2/2+O[x]^3.

Does anyone know what exactly might have caused this and how I could fix it without having to restart the kernel? (Presumably the previous call to SeriesCoefficient changed some obscure internal parameter in the kernel which may be reversible...)

I have a bunch of long, precalculated expressions in the kernel's memory and it would be quite annoying to have to export all of them and reimport into a new kernel.

Answer 1

Of course it's absolutely impossible to give a specific answer, so I can only remark that SeriesCoefficient works differently in version 9. For a list or array of functions, version 8 does not evaluate expressions like this:

SeriesCoefficient[{f[x], h[x]}, {x, 0, 2}]

but version 9 does. Maybe this causes problems somewhere in your expression. But really, I have no idea how else to track down your issue than to go through the list of incompatibilities between the versions one by one. This is the first that came to mind.