Here is what I found:
To resolve this problem, obtain Microsoft Office 2000 Service Release 1/1a (SR-1/SR-1a).
To obtain SR-1/SR-1a, click the article number below to view the article in the Microsoft Knowledge Base:
) OFF2000: How to Obtain and Install Microsoft Office 2000 Service Release 1/1a (SR-1/SR-1a)
The problem is that Access does not release memory until a script (vba) has finished running. Since 2000 and later are Unicode, the memory required is much greater than with 97.
You may have to split your code if this isn't the issue.
I was looking for a ReleaseBuffer() or ReleaseMemory() function, as in .NET, but didn't find anything.