If this is happening on only one user's machine, there is a chance that there is a damaged or missing file that somehow leads to the recursion that my colleagues mentioned.
The other possibility is that somehow a routine can call itself under some circumstances, and that in the case attempted by the user, that call incorrectly manages itself. You need to work with your user to see exactly what they attempted just before that error came up, because that will help you to locate the beginning of the path that leads to that condition.
One last thought: By any chance do you have a subroutine that attempts to pass an entire array or other complex object by value? The default for complex objects is by reference, but if you managed to pass a large object by value, Access has to copy that on the stack, which chews through stack space a lot.
One last question: Was the error specifically "Out of stack space" or did it include some mention of "Stack overlaps Heap" or similar wording?