Ive also seen this. No Aptana installed here
I also ran into this problem when I first tried Flash Builder 4. I had converted a large project from Flex 3. Next day when I tried to reproduce the problem I was unable to. Don't know what caused it or what happened to stop it.
yup, I know this error. I reproduced it several times.
If you use the automatic binding, by dragging and dropping an EntityService to a Datagrid, some code is added.
For example a definition for the callresponder, a call for this callresponder, a creationComplete for the DataGrid.
If you do this several times and then start you delete some parts of the generated code for bindinng, the described error happens quit quickly!
Then you do not(!) get a clear compile error, but it compiles for ever .
You can solve this in two ways.
Take this project out of your workspace ( you do not habe to delete it from disk).
Find the still existing code snip, that produces the error and delete it and use clean compile. To find the error is tricky!!! because DataGrid3 belongs to Callresponder 2 and so on and you don not(!) get clear messages from the compiler.
I use the automatic code generation, but do not use the automatic binding. Then this kind of error does not happen any more!
Hope this helps!
P.S: This has nothing to do with Aptana.