I'd suggest that you do an
. That will show you what your PATH variable currently is; it'll be a whole lot of directories, separated by colons. When you type in a command without a path, for example "ls", it will search through those directories, one by one, for a program entitled ls and run it.
Now if you try
again, you'll see that the PATH environment variable now has ":/opt/gnome/bin" stuck on the end, but is otherwise unchanged. (The colon is there to separate directories).
Using an equals instead of a colon will probably (I'm not quite sure here) result in it trying to look in a directory with a name something like /bin=/opt/gnome/bin every time it tries to run a command; since /bin= (presumably) doesn't exist, this will cause a problem. Especially as it's no longer looking in /bin (which includes, for example, ls); which can cause problems. (Your PATH might not have /bin at the end; it is merely used in an illustrative sense).
If you use
, then your path will only consist of /opt/gnome/bin. Now try something simple, like ls... and then it's probably a good idea to close that terminal and open a new one.