Problem w/ MZ-N505

[Skylab™]

Using LP4 mode the unit displays approx 320 mins of recording.

However, with about 100 mins left, the unit goes into edit mode and freezes. So I fiddled with all the buttons and nothing happened. I remove the battery and plug it back in, and the disk comes up blank!

I'm using Memorex MD 80 Crystal discs. Is this a problem with this brand of disc?

Using the Sony brand discs, I can simply let the disc fill up, and it will auto-save the recording.

e.g. I record my favorite radio show while I sleep, and in the morning, the disc is ready to go.

I have two unopened packages of the Memorex discs, and am most likely going to exchange them for the Sony's.

BTW, I'm using the TimeMark set at 5 min intervals. Perhaps the Memorex disc can only accept so many Time Marks?

any help is greatly appreciated.

Thanks.