Fail I haven't been able to install SI on U8.10 there are alot of problems with the Ubuntu 8.10 enviroment. Incorrect mysql_pdo modules etc... Nightmare ... SI installs fine on Fedora 10.

Problem: On Ubuntu 8.10 Server I get
"Warning: Smarty::include() [function.include]: Failed opening 'cache/%%4E^4ED^4ED298BA%%footer.tpl.php' for inclusion (include_path='.;c:\php\includes:./include') in /srv/simpleinvoices/include/smarty/Smarty.class.php on line 1258"

Cause: php.ini has a Microsoft Windows include path in it that shouldn't be there:

vi /etc/php5/apache2/php.ini
# this is what it looks like before
; UNIX: "/path1:/path2"
include_path = ".:/usr/share/php"
;
; Windows: "\path1;\path2"
include_path = ".;c:\php\includes"
Fix:
Open and comment it out
# this is what it should look like after fixing
; UNIX: "/path1:/path2"
include_path = ".:/usr/share/php"
;
; Windows: "\path1;\path2"
;include_path = ".;c:\php\includes"