I hate to tell you this.... I don't use ANY of those plugins, so I have practically no idea what to tell you.
For the backup thing, just make sure if you insist on using it that your wp-content folder is set permitted to 777. You don't need the plugin really, all you need to do is use phpmyadmin through your host control panel to get db backups.
Only thing I can think is that there are conflicts between all of them. You can try deactivating them all, then activate sk first, then akismet, then check the permissions on wp-content, make sure they're 777, then activate it. If you still get errors, repeat above procedure in different combinations until you've tried them all.
And you probably want to deactivate ALL your other plugins before you start on this....
I really do apologize; this is one of the areas I'm not ever going to be much use on I'm afraid.
Tell you what, give the deactivate etc. a try, and report back, but start a new thread, okay? And it's pretty late for me already, so if I don't catch up to you before morning I'm not ignoring you - I WILL check up tomorrow!