Confused at build error

Hello, i have a small ant build file that i wrote a little while ago, it's always worked fine but now it has started to give me errors. With the -debug arg i get

[javac]Compiling 2 source files
....
[javac]     sourcefile1.java
    [javac]    scorcefile2.java
    [javac] scorcefile3.java:5: package packageName does not exist
    [javac] import packageName.className;

I can see that it's compiling the sourcefile1 & 2 files, which its ment too, but then finds an error with source file 3 which isnt referenced by either sourcefile 1 or 2 and brings the total source files to compile to 3. What could be causing this?

Thanks,