Runtime creation of Advantage TAdstables causing access violations.

I hope that some-one can help.

What I'm trying to do is to open an Advantage database table inside a
DLL using the following code:

tbl := TAdstable.Create(nil);

Using 'nil' because it isn't attached to any TComponents. However,
when I exit the application, it creates an Access violation.

If I replace TAdstable with just a normal TTable (tbl :=
TTable.Create(nil);), then everything is fine - no Access violation on
exit.

Can anyone suggest how I can fix this?

Many thanks,
Nick