Have you found a resolution to your problem? I am having the same issue, except I am trying to import mx.data.DataService and other mx.data classes. I've posted a few times on here but can't ever get a response.
I had a flex 2 app which worked great with flex data services, but as of flash player 9.0.115 it doesn't want to work. I've tried recompiling into flex 3 but all the mx.data packages and classes are gone and I can't find any documentation on it either.
I have the same problem to you too. I look into the Flex 3 Language Reference and found the mx.data.DataService was gone and I don't understand why adobe do that. Now I have a question "If I can't invoke <mx:DataService>, how can I use data management service of LiveCycle Data Service ES? and another question "If I can't use data management service, what the benefit of using Flex 3 with LCDS because BlazeDS can do the same thing so why I have to spend my money to this product?"
I use all of my energy to look for the answer of this but I can only found the solution that use the Flex 2 so I guess that LiveCycle Data Service is work well only on Flex 2, am I right?
First go to your Flex project properties > build path > properties, and make sure the fds.swc and playerfds.swc are correctly linked - they should be if you used the project wizard correctly.
<mx:DataService> is under package mx.data.mxml.
As for LCDS vs BlazeDS, LCDS supports data management service. The data management service use a model oriented approach, which is ideal for data driven, collaborative types of apps. It's a bit difficult to explain in one sentence since there's nothing like it on the market, but if you vest some time ramping up on it, it is guaranteed to save you time down the road.
It's my fault from the installation phase of LCDS, I use the J2EE server choice instead of JRUN. So when I start the new Flex & LCDS Project and when I typed <mx:DataService> in editor the error will wait for me.
When I reinstall with integrated JRUN option it work fine so the next stage for me is what wrong with TOMCAT 6 for LCDS because I already make the necessary process for install LCDS in TOMCAT (involve install JOTM in TOMCAT 6). When I run the samples application of LCDS in TOMCAT it has many error in backgound while it work fine in JRUN but in the production deployment phase I want to use TOMCAT.
I just want the "Data management Service" feature was integrate in BlazeDS but I know that feature was the "main actor" of LCDS so I hope Adobe will release the next BlazeDS with this feature in it.
I feel very impressive for the DMS feature. It make me feel the difference about "Web App." (or RIA). I fulfill my passion about data handle software topic I don't ever seen something like this one before. I just think that new policy about LCDS marketing that stop Express Editor of this product will screen most people from this greate product. So, I beg Adobe please release LiveCycle Data Service ES 2.6 Express Editor and I will love you forever :).