Maybe something is wrong with the SonicStage database file. The file is located in the "C:\Documents and Settings\All Users\Application Data\Sony Corporation\SonicStage\Packages" folder and is called MtData.mdb (there may be other files with similar names there, e.g. MtData1.mdb, $$MtData.mdb, etc., which are backup copies of the main database). Try moving the file away to a different location, and delete any backup copies (but don't delete the MtType.mdb file). Then start SonicStage, and it will create a new empty database. Then try importing music into this new database.
Wincue is useless for gapless albums, since it introduces silence where it shouldn't be. I am using a set-top DVD-player with an optical out to record in SP, so the DG2 that I bought last year is just a piece of equipment in my collection.
The switch on the "first" version of the DG2 had something to do with trackmarks (setting different modes, IIRC). My "switchless" version doesn't transfer trackmarks on non-stop albums at all. And for albums with separate tracks and long enough pauses between them trackmarks are created automatically by the recording unit, even if they are not properly transmitted via optical.
I have a DG2 of the later (switchless) variety, and it looks like it is not possible to preserve original CD trackmarks when recording through it, i.e., the signal is being changed, compared to the original CD. I've tried various software players and output modes (e.g., kernel-streaming), all to no avail.
I have encountered brief dropouts of music when played directly from SonicStage in Windows XP. Not sure what causes this - drivers, DirectX, codecs, buffering problems or some other system settings. But all these files play perfectly when transferred to a Hi-MD.
Even after the "Track properties cannot be edited..." message, SonicStage should display the Track Properties dialog box, with all four tabs accessible in read-only mode. So you may determine the location and format of the physical files, and check what's wrong with them (e.g., whether they are marked as read-only).
You need to determine exactly the filetype and the rights info. In SonicStage, right-click a file that doesn't transfer anymore, then select Properties and check the "Rights info/Additional info" and "File Info" tabs.
And which version of SonicStage are you using? The one supplied with the RH710 is quite old (3.0, IIRC), so it still has all the DRM craziness.
Just remembered: make sure that the Microsoft PCM Converter audio codec is enabled on your PC. It tends to get disabled sometimes, and this may cause problems with SonicStage, since it is used for several purposes (format conversion, etc.).
SonicStage automatically applies copy protection to anything uploaded. This is an atavism of SONY's DRM paranoia. To remove copy protection, you need to close SonicStage and then run the SonicStage File Convertion Tool and unselect the Add copy protection checkbox. After a few minutes (the time depends on the amount of music in your library) it will create unprotected copies of all your uploaded tracks.
It is a good idea to run this tool with the checkbox unselected after uploading each disc, so that you always have unprotected copies of all your files.