Bizarre Final Cut Pro Problem

[animal]

Hoping one of you experts can help.

Using an Emac 10.2.8, older Firewire 120GB hard drive, FCP 4.1, Canon 
XM1 (Like GL1)

Up until Monday, I had no problem downloading dv to either the Emac or 
a couple older external 120GB firewire hard drives.

Now - if I download 6 minutes or more to an external, I take the risk 
of having the computer's color wheel spin forever.  What is happening 
is that every so often the 900MB or so clip is downloaded as a 65 - 98  
GB clip and overloads my system.  Each time the external hard drive is 
left with 1.43GB.  I erased this external drive only 7 to 10 days ago, 
and am fairly certain it worked for downloading before Monday.  Then I 
try force quit after force quit which usually but not always works.  
After restart, I then trash the massive clip and start again but waste 
huge amounts of time.  It even happened with a shorter 4 minute clip 
once.

The Emac seems to run fine otherwise except slower after each of these 
incidents.

Thanks for any suggestions
Lynn