Jar reloading broken in IDEA 5.1.2?

I'm going crazy with IDEA 5.1.2 (build 4267). For some reason, jar reloading seems to be broken now. Here's the behavior I'm seeing...

Project B depends on jars from another project A. It used to be that I could modify the classes in project A, do an Ant build which generates new jars, and then project A would automatically pick up the changes. Now, however, the new jars are totally hosed. Actually, the new jars themselves are fine--it's really only IDEA's cached versions that are broken. The only way I've found to fix things is close IDEA and delete the appropriate directories under \.IntelliJIdea50\system\caches and the appropriate jars under \.IntelliJIdea50\system\jars.

By "totally hosed", I mean that viewing the classes using IDEA's decompiler results in classes that look like this:

class _
{
}

I've also attached a screenshot of what I see for the broken jar in the Project tab.

Anyone else seeing this? Is this a bug? Is there a workaround?

I'm using IDEA build 4267 with Sun JDK 1.5.0_06-b05 on WinXP sp 2.

thanks!

chris