I have encountered this a few times within the past few weeks.  I will be working on an existing Java class which has
several import statements and will add a reference to another class for the first time.  When I press Ctrl+Shift+I (fix
imports), many of my existing import statements are corrupted.  

For example, here is what it might look like before:

import com.example.mypackage.MyClassOne;
import com.example.mypackage.MyClassTwo;
import com.example.mypackage.MyClassThree;
import com.example.another.package.Foo;
import com.example.another.package.Bar;

Here is what it would look like afterwards:

impoimport com.example.mypackage.MyClassOne;
imimport com.example.mypackage.MyClassTwo;
import com.example.mypackage.MyClassThree;
import c com.example.another.package.Foo;
import com.example.another.package.BarBar;

It does not happen consistently so I can't say exactly what causes it sometimes but not others.  But it does happen
fairly often (every 2-3 days or so).

Here is the configuration I have noticed it under; I am using the Java SE IDE and have installed all updates available
through the AUC:

Product Version: NetBeans IDE 6.5 (Build 200811100001)
Java: 1.6.0_10; Java HotSpot(TM) Client VM 11.0-b15
System: Windows XP version 5.1 running on x86; Cp1252; en_US (nb)
Userdir: C:\Documents and Settings\tq232c\.netbeans\6.5