Yesterday I was doing some web and eCommerce development for a client in Kildare, I was working to link Expression Engine and FoxEE up to foxycart. When testing transactions everything seemed to work ok, except that after very transaction I received the following error:
DataFeed Failed: (2134029) 2010-09-30 05:50:28 No data returned for http://www.blahblahblah.com/index.php?ACT=24 
Every time the error occurred foxycart would send me an email.
The XML datafeed sends transaction data back to the expression engine website and FoxEE so that FoxEE can display the transaction details in the admin interface. Despite the error the transactions were being properly displayed by FoxEE and everything else seemed to work well!
Any script that consumes the foxycart XML datafeed must return the text ‘foxy’, if not this error will occur. It turns out that if your expression engine site is offline (Admin / System preferences / General Preferences / Is system on? == No), FoxEE will return some testing text instead of ‘foxee’ and so the error will occur. The funny thing was that my website was not ‘offline’ it was completely live and so FoxEE should not have been in test mode at all…… strange…. Then I remembered that I did have the site offline a few days ago but not now….
Well I cleared all of the Expression Engine caches and the error went away!!
Hope this helps somebody with a similar quandary – If you get this error, try:
(a) Check that your site us ‘On’
(b) Clear the Expression Engine Cache (Admin / Utilities / Clear Cached Data)