You may remember that Lightroom 1.4 was released not so long ago (along with a Camera RAW plugin). About those updates, yeah, you can’t get them anymore. From Macworld:
According to Adobe Lightroom product manager Tom Hogarty, the updated releases both contain an EXIF time stamp error and a conversion error for Olympus JPEG files. The updates also cause a DNG conversion error, though that issue is limited specifically to the Windows releases.
Oops. Downgrade instructions are available on one of Adobe’s blogs. This is a bit of a blackeye, especially considering they deemed it a big enough bug to pull it from their website.
One of the problems is an error importing Olympus DSLR JPG files. (I have an E-510 but I understand other models are also affected). The previews are corrupted with a picture-in-picture of the original. The original file is not corrupted and if you downgrade to v1.3.1 the previews can be fixed.