i did mean create a new one, i have not used the spliter myself.
The error message i am unsure. Try going into one of your form, and then go directly to the code, and compile it. Sometimes a mde file will not be created due to a error within the code. That could be it.
But saying its to large, could mean something else altogether.
As a last result, you could try creating an mde file with all the table empty, and see what happens then, but it should work, i've created an mde file with more then 15 tables with no issues. But if you split the db, then you would only be creating an mde file with linked tables only.
Hope this helps.