file copying - C# Disc eject randomly fails saying the session has to close (not even burning a disc) -

my users have been having annoying issue lately.

i've got app takes images cd, dvd, or usb drive , copies them network.

when it's done copying should automatically eject disc.

the problem is, when disc done being copied , goes eject, takes long time. 1 of users said waited hour finish closing , eject.

on other discs has happened, user try hit physical eject button , bubble on windows 7 pops , says please wait until session closed before ejecting.

nothing being burned disc , disc not cd-rw or dvd-rw don't understand why needs close session on disc.

is possible person burned cd messed somehow?

out of 250+ discs have gone through far today, happened on 2 of them leads me believe wrong these discs.

here's method ejects drive:

    private void eject()     {         try         {             volumedeviceclass volumedeviceclass = new volumedeviceclass();              foreach (volume device in volumedeviceclass.devices)             {                 if (!device.isusb)                     continue;                  if (device.logicaldrive == null || (device.logicaldrive.length == 0))                     continue;                  /* should down here if our device usb drive */                 device.eject(true);             }              var sb = new stringbuilder();              mcisendstring("open " + _drivename.substring(0, 2) + " type cdaudio alias cddrive", sb, 127, intptr.zero);             mcisendstring("set cddrive door open", sb, 127, intptr.zero);         }         catch (exception ex)         {             ex.log(ex.message, logger.severity.error, "error ejecting cd drive: " + environment.machinename);         }     }