can't find large files >4GB for recovery

I'm using WinXP 64bit SR2 with Recuva 1.27.419 (in taskmanager shown as Recuva.exe *32)

acidentially I deleted a couple of large Files (each has a size of 8GB) on a 500GB NTFS Partition. No Changes were made to this Partition after deletion.

So I gave recuva 1.27.419 a chance. All Files acidentially deleted below 4GB were shown with a "Ecellent" recovery state, but the large files were not shown in the Filelist. I've restartet recuva an retried it with "Deep Scan" method, but got the same result.

Any hints?