Content encoding errors with Firefox

[subBlue]

A few of our clients have been reporting that sometimes their sites throw errors in their browser saying:

Content Encoding Error
The page you are trying to view cannot be shown because it uses an
invalid or unsupported form of compression.

Interestingly it only seems to be happening on Firefox 2 & 3+.
It's been reported sporadically on a couple of our servers with LS 3.3.24 ent and LS 4.0.10 ent. We are using the default gzip options:

Enable Compression: Yes
Enable Dynamic Compression	: Yes
Compression Level (Dynamic Content): 1
Compressible Types: text/*, application/x-javascript
Auto Update Static: Yes
Static GZIP Cache Directory: Not Set
Compression Level (Static File): 6
Max Static File Size (bytes): 1M
Min Static File Size (bytes): 300

Most of our sites use Ruby on Rails but we use page caching extensively and then serve up the static html pages via rewrite rules such as:

RewriteCond %{HTTP_HOST} ^www\.host\.com [NC]
RewriteRule ^$ cache/www.host.com/index.html [QSA]

RewriteCond %{HTTP_HOST} ^www\. host\.com [NC]
RewriteRule ^([^.]+)$ cache/www.host.com/$1/index.html [QSA]

It's like the static cached version of the page is corrupted as it only affects one or two pages in the site and disappears once the cache gets automatically updated,

Has anyone seen similar behaviour?