Can you see any of the sessions? If so - which one?
From Nero 5.5 Help:
Q. Although I created a Multisession disc I can only see the last session. Why?
A. If your CD Recorder supports multisession, you can only read the last session of your CD on Windows 95/98and NT 4.0 and the first session on Windows 3.1x.
Nero gives you the solution: in Windows 95/98and NT 4.0, you can use the Nero Multi Mounter to switch to any other session of your Multisession CD.
Were sessions linked/imported each time you added one to the disc you're trying to read?
From Easy CD Creator 5 basic Help:
multisession
A method of adding data incrementally to a CD in more than one recording session. If data is linked between session, all data on a multisession CD, when read on a multisession CD-ROM drive, may be seen as part of a single logical structure. Multisession is very different from packet writing.
multivolume
A CD containing multiple sessions that are not linked together, so that each "volume" on the CD must be read as if it were a separate CD. You can read different sessions on a CD using Session Selector in Easy CD Creator Deluxe.
Importing a Session
Normally, you can access only the last session written on a multisession CD. To import a specific session on a multisession CD into your data CD project, follow these steps:
1. From the CD menu, select Import Session.
2. Select the session you want to import from the list and click Import.
Using Session Selector
Session Selector allows you to select and access different sessions on a multisession CD. Normally, you can access only the last session written on a multisession CD.
To run Session Selector:
Click Start, point to Programs, point to Roxio Easy CD Creator 5, point to Applications, and then select Session Selector.
Problems Reading Multisession CDs
If you can see only data recorded in the first session on the CD but not in subsequent sessions, it may be that:
.You recorded the CD in CD-ROM (Mode 1) format, while your multisession CD-ROM drive only recognizes CD-ROM XA (Mode 2) multisession CDs.
.Your CD-ROM drive does not support multisession at all.
If all this is correct, it seems you must have something like multimounter/sessionselector installed to read either multi-session or multi-volume CDs in Windows 98.
Troubleshooting Guide for NTI CD-Maker 2000
http://www.ntius.com/default.asp?p=support/support_main
NTI
Incremental Multisession
Incremental Multisession recording links existing sessions with a new session being written to the disc. Data from a previous session can be accessed since the each session has links to the data written in the previous session.
Independent Multisession
Independent Multisession recording organizes multiple sessions as completely separate volumes, each with its own directory of information. In most cases, you will need a utility such as Session Explorer to view data from a previously recorded session on the disc.
So maybe 'Session Explorer' was installed automagically when you installed NTI CD-Maker and it's been messed up somehow?