Just remodded and textured my minecraft, can't use MP

[Leviatharan]

I figured it was long enough after the 1.0 release that I could re-mod my minecraft.jar files with Equivalent Exchange, Portal Gun, etc. and the support files for them. Back before the release, my multiplayer server was perfectly fine with me having mods in single-player, and so I figured the two were completely separate. I don't have any mods on the multiplayer server itself- just the Essentials bukkit plugin.
Well, today I decided to try out two new mods (Animal Bikes and Thaumcraft), looked up how to install them, did so, logged into minecraft, made a new single-player world and... everything worked just fine! No blackscreens, whatever.
Then I realized that I'd lost my texture packs during the modding, so I used MCPatcher (gave me the usual 'your minecraft.jar is already modded, yada yada'), recreated my Dokucraft and put it into the texture pack folder.

This... is where things started messing up.

I turned on Dokucraft (background immediately changed as usual), hit 'okay', and... black screen. But that's fine, I turned Minecraft back on, logged in, turned on my single-player and lo and behold everything's working as intended.
I fired up my multiplayer server. I tried to quit to title from my single-player but it just blackscreened again, go figure. Started Minecraft again, logged in, added "localhost" to my multiplayer selection screen and when I logged into it... THAT'S where everything was completely screwed. It blackscreened again.
Cue the process repeating over and over until I'm typing this here now.

Where did I go wrong? Did Dokucraft screw me over? Should I have used MCPatcher before modding? Did one of my new single-player mods break my Minecraft so thoroughly I can't get into multiplayer?

---------- Post added 2012-01-07 at 03:37 PM ----------

Removed Dokucraft from my texturepacks folder, problem still persists, so I guess it's not that...

---------- Post added 2012-01-07 at 03:42 PM ----------

Deleted my minecraft.jar, restarted Minecraft, used MCPatcher, threw in Dokucraft, got into my multiplayer server just fine.
Downside is that now I can't mod anything because I can't find my frelling Meta-Inf!

---------- Post added 2012-01-07 at 03:50 PM ----------

Alright, found the Meta-Inf (MCPatcher has an annoying ability to clone my minecraft.jar and put the Meta-Inf in the clone... hmph). Server's now accessible, single-player is...
...
Still unmodded. Dammit.

[PizzaSHARK]

If you're using MC Patcher, just have two setups for your minecraft.jar. Have one with only tested, SMP-compatible mods, and have another with all the mods you want. When you wanna play SMP, use the SMP setup. When you wanna play SSP, use the SSP one.

I'd recommend just deleting your entire Minecraft folder to ensure everything's cleaned out.

[b00rz]

Some new mods now require you to use Java7 or else you will experience black screens on load or closing of maps. Also not all mods are compatible with each other or MCPatcher you should check the compatibility on the sites from you got the mods from.

Only other thing I can suggest is that you install the mods 1 at a time and see where the error comes up. I did used to have a .BAT file that would run minecraft in a debug state and it would show where the error came from but unfortunately that hasn't worked properly since 1.8 =(