Drupal Site - Files Won't Attach (upload) To Content On Custom Domain, but works fine on zymichost subdomain

[elmerato]

I have a Drupal-based site on a subdomain in zymichost.com. Had a subdomain on my domain have its "A" record (I can't touch the nameservers) point to the zymichost subdomain such that for example "sub.mydomain.com" points to "sub.zymichost.com".

Everything works like a charm except when I try using upload module of Drupal on my domain.
I can upload files fine under "sub.zymichost.com" but i get nothing or "file upload error" on "sub.mydomain.com".

I believe this is an .htaccess issue but I don't know the right way to work out Rewrite rules.

Looking forward to some assistance. Thanks.

[elmerato]

Resolving my own issue.

I found a workaround which consisted of the following:

1. Removed "A" record and instead used web forward (URL cloaking) to point sub.mydomain.com to sub.zymichost.com.
2. In .htaccess file at root of webfolder, added a slash to index.php entry near the bottom of the file as described http://www.zymic.com/forum/index.php?showt...&hl=#"" target="_blank" rel="nofollow">here.
3. In settings.php, uncommented base_url as "sub.mydomain.com".

This allowed files to be uploaded/attached via Drupal's upload module.

However, there is a side-effect to this - update.php and views editing (I suspect there may be others) won't work. Temporarily disabling clean-url and commenting-out base-url in settings.php during updates and editing clears things up. After performing updates or editing of views, simply enable the above items again.

If others in the community can come up with a more appropriate approach to this issue, please post them here.
Thank you.