Your comments

Did you get an error message when you tried to upload the file? What kind of file are you trying to update? Did you try to load the site in Safari? Maybe it's a caching issue.
Can you please send an example file with demonstrates the problem to support@textasticapp.com? I can't reproduce it.
You can download the manual as a PDF file from http://www.textasticapp.com/v4/manual/textastic_manual.pdf  and use iBooks or another PDF reader to read it on your iPad.
The next version will allow you to import pictures from the Photo library.
The next version will support zip and unzip.

You could try to use the "ASP vb.NET" syntax highlighting definition. You can select this definition in the File Properties popover after you opened the file. 

It looks interesting, but judging by the Readme, it probably won't support many real life configurations - i.e. modern authentication methods. Also, the last library change was a year ago.
It's great to hear that it's working for you now.