Unable to highlight/copy text in iPhone Safari on mobile site

I have a mobile site which I'm testing on the iPhone, and unlike most other sites, I'm not able to hold my finger on the screen to get the 'copy' menu to appear (with the draggable handles to select an area to copy). Nothing happens at all on my site.

I've tried adding the following to my style sheet but it hasn't made any difference:

-webkit-user-select: text;

I should also state that I have the following also in my style sheet and within the page head:

-webkit-text-size-adjust: none;

I've got these as I didn't want the content to be scalable, and just wanted the content to span 100% of the device width.

Would the implementation of any of the above be causing the lack of selectable text on the site? Out of interest, I tried the flickr mobile website which also is not scalable and uses 100% of the device width like my site, and that also doesn't seem to come up with the draggable/select area for copying when you hold your finger on some text.

Does anyone have any idea why this is or how I can make the text content (or any content actually) selectable for copying/pasting?

Thanks

are there any elements that may be obscuring the items by overlaying them, etc? a z-indexing issue, perhaps?