Well, here's details on the BESTFIT bug, confirmed on GX Revs M and P, and may be present in SX Rev E to a different extent. I want to see the bug: 1. Put a 2*2 or other two dimentional array in SigmaDat. 2. Find the softkey for BESTFIT. On a GX this would be purple-5, SigmaPar softkey, then MODL softkey. 3. Press it a few times quickly and the bug will occur. What Happens: 1. Warmstart 2. Sometimes SigmaDat is erased. How in the world did I find something THIS silly: Well, I often use the STATs application and noticed a warmsarts sometimes around the time I use BESTFIT. I noticed that it happened when I was in a hurry, and after a bit of searching I found it. This bug is much worse than the FFT bug for a few reasons. You can get a warmstart ith BESTFIT unintentionally, and BESTFIT is typically more often used than FFT. I haven't looked at the code but according to WSLOG it seems that the bug is very similar to the FFT bug. Apparently it is a hardware stack overflow. (that is what the FFT/IFFT bug is) Seems to me that doing the similar on an SX will not cause a warm start, but rather pressing BESTFIT fast will leave useless reals on the stack. The SX bug is NOT confirmed though. The GX bug is confirmed. Maybe someone with a Rev R can tell us if this bug is in Rev. R? :) And SX owners can try this on their machines as well if they like. Regards, Boris