disappearing disk space

[Dr. Trevor J. Hutley]

Al 1.25/15.2" OS X 10.3.2

It happened for the second time, last night: my main partition (boot 
paertition) which has about 1.55Gb of free space, behaved as if there 
was no space.  It even showed 0 bytes free.  I could not save my open 
documents to this partition.  How did this free space suddenly 
disappear?  And what should I have done about it?

I tried restarting a few times.
I tried to start up in single user mode (cmd-S) but this did not work.
I tried to zap the PRAM, but the key combination did nothing.
The Apple logo had turned in to a grey fuzzy square.
I put in a bootable CD with some utilties, but cmd-C would not work, 
to cause boooting from the CD.
After a few more restarts, I had my free space back, the Apple logo 
had reappeared, and everything seems fine.

What was that ???

Has anyone else seen this freaky kind of thing?

regards,  Trevor