And include the specs on the external drive. On an old system like yours, USB 1 is too slow. If its firewire, how fast is the drive and how full is it. Its bad practice to let a recording drive get more than maybe 3/4 full(so try moving any finished sessions onto a backup drive). If the firewire drive is 5400 rpm, its too slow for recording, period. Sure it may have worked for a while, but many unsupported things work....."for a while"
Beyond that, the computer specs are barely adequate, even for LE 8. It might also help diagnoses to know what interface you have and the session settings(sample rate and bit depth)
What happens at 5:10 in the song? Have you set the playback buffer to 1024?
As a "hail Mary" to complete the project, try making half the tracks inactive and bounce. The enable the inactive tracks and make the other half inactive and bounce again. Import those 2 stereo audio files into a new session and bounce to get the desired final mix(for sure, this is a PITA, but anything is worth it to finish something that needs to be done).