Any workarounds for TRAC #1488131? (Safari and PDF attach)

[ABerglund]

#1488131 (Safari 5 with Adobe Reader plugin can't display PDF attachments inline)

Since we moved from 0.5.4 to 0.6, we've seen that Macs with OS 10.5 (Safari 5) with the Adobe PDF viewer plugin installed receive session errors when attempting to view PDF attachments inline. Firefox does not exhibit the problem. Installed today's SVN, same issue. Using 0.5.4 still works as expected.

Looking for suggestions for workarounds or solutions to this ticket. Since our server does webmail for 14 K-12 school districts (with a heavy percentage of Macs), this is a hot topic around here.