I just signed up to ask about the very same thing, our error log was 6GB.
We are currently running WordPress 3.5 and the DM plugin was working perfectly, but today on updating DM to 2.3.8 lots of errors are being generated: PHP Warning: fread(): Length parameter must be greater than 0 in /wp-content/plugins/download-manager/process.php on line 249.
Process ine 249 is: echo fread($file, $wpdm_chunk);
The only other change on the site today was updating the Jetpack plugin to 2.2.1.
We have had to disable the DM to get the site back up, but would love to get it working properly again as it was running just great. Any advice?