Re:

martin:
couple o things:

use something like sed to pre process the file taking out the erronous
data, if you know what the bad data is

one thing i use sed for is html escape single quotes and the like,

it should work well for you

the regex for substituting like that is:
s/old/new/g

the sed command operates regexes with an -e switch :

sed -e s/error/correction/g errorfile>correctedfile
takes errorfile in and changes any occurence of 'error' to 'correction'
and
prints all data to correctedfile

also if its a flat file you could just use the copy command in psql
instead of inserts:

\copy tablein from filename