i buggered up my comments for the last few days - incase anyone was wondering why they weren't working (i just thought nobody loved me - i should have guessed something was up by the lack of comment spam!).

update: i thought i'd catalog here for future reference what the problem was, seeing as i couldn't find a solution through google, but had to figure it out for myself (not that it was that difficult)...

the error i was getting was something like this:

Invalid [] range "l-e" in regex; marked by <-- HERE in m/ http://xxx.org/#viagra|-casino|-com.com|-xx-xx.org |-xxx\.com|-xx\.net|-xx\.|-xx.info|.+xxx.+os.com |.+xx.com|.xx.ro|.xx.ro|0 at extlib/jayallen/Blacklist.pm line 3098.

and the reason i was getting this error was because i had added a url containing a square bracket to my blacklist of 'disallowed' urls - can't remember if it was right or left - but one of these: ], [

so, after much consternation and head scratching, i remembered that i could edit the list of urls from an interface (mt-blacklist.cgi - that was provided with the blacklist plugin that i had completely forgotten about). so i removed the offending url and everything worked fine again. and so it goes.