Server will not start up

[MyCatFishSteve]

I a experienced server owner and I run my servers on my iMac Snow Lion and I upgraded to 1.5.1 server files and when I run it it gives me this error

Last login: Sun Jun 9 14:58:07 on ttys001

Username-iMac:~ User$ /Users/User/Desktop/Minecraft Servers/Tekkit server/Start.command ; exit;

Exception in thread "main" java.lang.NoClassDefFoundError: ab

at java.lang.ClassLoader.defineClass1(Native Method)

at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)

at java.lang.ClassLoader.defineClass(ClassLoader.java:615)

at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)

at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)

at java.net.URLClassLoader.access$000(URLClassLoader.java:58)

at java.net.URLClassLoader$1.run(URLClassLoader.java:197)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:190)

at java.lang.ClassLoader.loadClass(ClassLoader.java:306)

at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)

at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

Caused by: java.lang.ClassNotFoundException: ab

at java.net.URLClassLoader$1.run(URLClassLoader.java:202)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:190)

at java.lang.ClassLoader.loadClass(ClassLoader.java:306)

at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)

at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

... 12 more

logout

[Process completed]

I have admin privileges set on my start up commands and before the big updates NetherOre's wouldnt run on the server I fixed it by removing the mod and now I removed it again and it wont run. The client runs fine, the server is the problem. I have Java 7, do I need to downgrade?

I tried removing all the mods but it gives me errors still

Exception in thread "main" java.lang.NoClassDefFoundError: ab

at java.lang.ClassLoader.defineClass1(Native Method)

at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)

at java.lang.ClassLoader.defineClass(ClassLoader.java:615)

at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)

at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)

at java.net.URLClassLoader.access$000(URLClassLoader.java:58)

at java.net.URLClassLoader$1.run(URLClassLoader.java:197)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:190)

at java.lang.ClassLoader.loadClass(ClassLoader.java:306)

at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)

at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

Caused by: java.lang.ClassNotFoundException: ab

at java.net.URLClassLoader$1.run(URLClassLoader.java:202)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:190)

at java.lang.ClassLoader.loadClass(ClassLoader.java:306)

at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)

at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

... 12 more

logout

[Process completed]

[TekkitNoodle]

I found this problem. I deleted the nether world folder. Then restarted the server with the netherore.jar in again. Seemed to do the trick for me!