Have been using 3.30-RC6.  I updated several captures 
produced in previous HTTrack versions, and was getting the 
following error.  Is this something to worry about?
Error:  Cache: version 1.4 not supported, ignoring current 
cache


Also, I noticed this odd one:

Error:  "" (0) at link www.tas.gov.au/images/head_rightbg.
jpg (from www.tas.gov.au/style_tol_v2_advanced.css)

I suspected it was a problem with the new "relative CSS and 
JS" functionality... so I tried to develop a test case to 
confirm this, but so far I can't produce a test case where I 
can replicate the problem.

It is an odd error.  Perhaps it makes more sense to you.