From /usr/share/doc/plymouth/README.Debian:
Disabling the splash screen
---------------------------
There are two methods to disable the splash screen. Both have the
same effect. Your boot will show such messages as are emitted by
the starting services, and will still be able to prompt if needs be.
1) Remove all of the plymouth-theme-* packages from your system,
including the text ones. Plymouth will remain installed to
permit boot-time prompts.
2) Remove "splash" from the kernel command-line. You can do this
per-boot, or make it permanent by changing the
GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub
I suggest you remove the additional themes you have been installing, as these have messed up your system. After you have done that, I suggest you open Package Manager and select to re-install the plymouth package, just to be sure. On a clean Linux Mint 11 install, only the following Plymouth packages are installed:
- libplymouth2
- plymouth
- plymouth-label
- plymouth-theme-text
- plymouth-theme-ubuntu-logo
- plymouth-theme-ubuntu-text