Roach
Does your mouse wheel work with other software (IE or other)
I had a look at the Opera support pages and found a rather cryptic parameter that might help.
"YNPStickInstalledOverride" to be added in the Opera6.ini file in the [user preferences] section.
This requires that your can find the file and use a text editor (Notepad or Wordpad will do).
I'm not sure if this can help, but at least it seems to be inoccuous (sp?) in my case.
Insert "YNPStickInstalledOverride=0" (one line) at the end of the [user preferences] section of the file. Don't know what values are appropriate (would try 0 & 1).
see
http://www.opera.com/support/usingopera/operaini/ for more details
Good luck