well, this is the full diff (excluding readme.txt);
diff -x '*svn*' -x readme.txt -r 1.6.3/autoptimize.php 1.6.4/autoptimize.php
6c6
< Version: 1.6.3
---
> Version: 1.6.4
29d28
< // update_option('autoptimize_version','none');
31c30
< $autoptimize_version="1.6.3";
---
> $autoptimize_version="1.6.4";
50c49
< // if (!is_user_logged_in()) {
---
> if (!is_feed()) {
93c92
< // }
---
> }
diff -x '*svn*' -x readme.txt -r 1.6.3/classes/autoptimizeHTML.php 1.6.4/classes/autoptimizeHTML.php
35c35
< if ($restore_mfuncs) {
---
> if (isset($restore_mfuncs)) {
diff -x '*svn*' -x readme.txt -r 1.6.3/classes/autoptimizeScripts.php 1.6.4/classes/autoptimizeScripts.php
30c30
< $exclJSArr = array_map('trim',explode(",",$excludeJS));
---
> $exclJSArr = array_filter(array_map('trim',explode(",",$excludeJS)));As I wrote, nothing spectacular in there, very surprised about your wsod as well.
What you could do (I would if I could reproduce the problem, but I can't), as last resort, is restore the isset-thing in autoptimizeHTML.php and revert the other 2 changes from the diff above one after the other to see if you can isolate the culprit that way?