Len-
Sorry, I unintentionally lied. I thought the "memory free" showed up in red when it was negative, but my memory failed me. It doesn't seem like it shows up in red, but it does show the negative sign.
This is a screenshot after loading in FACTORY.esx (there are still 87.5 seconds of space available):

Then I dragged-and-dropped a bunch of other files to get this:

In the 2nd screenshot there are -62.9 seconds of space available meaning that I need to delete 62.9 seconds of samples before I can save the file.
I know this is pretty frustrating. So what I should have referred to in my last email was the "Memory Free" text above the table that lists all the samples. If that's ever negative, then you won't be able to save the file until you get the "Memory Free" to be a positive number (or 0).
I started working on a new version a while back, but a few things have prevented me from finishing. Hopefully I can focus on this again.
If you are still having issues, send me an email, and maybe I can help debug what the problem is.
Good luck!