[ BUILD # : 201110140600 ]
[ JDK VERSION : 1.6.26 ]

For large XML documents, when I try to validate two documents in succession,
the second attempt before the first has finished, the validation output appears
in the same output pane ("XML Check"). When the second validation is started,
the output window is cleared, and then the output from both validation attempts
are written to the output window, with no obvious indication which document the
errors/messages are from. The same is true for multiple validation checks on
the same file: previous checks are not cancelled, and output from all checks
appears in the same console.

To replicate (two schema scenario):
1. Get two big XML documents that reference XML schemata.
2. Validate one (Right-Click > Validate XML)
3. Look in the output window pane "XML Check": the check has started
4. Quickly validate the other, before the first validation attempt has finished
(Right-Click > Validate XML)
5. Look in the output window pane "XML Check": only the second validation
attempt's start messages are visible. Then "XML validation finished appears
twice in the console.

To replicate (one schema scenario):
1. Get a big XML document that references an XML schema.
2. Validate it (Right-Click > Validate XML)
3. Look in the output window pane "XML Check": the check has started
4. Quickly validate it again, before the first validation attempt has finished
(Right-Click > Validate XML)
5. Look in the output window pane "XML Check": only the second validation
attempt's start messages are visible. Then "XML validation finished appears
twice in the console.
6. Repeat 1-5 with three or more concurrent validation attempts. Sometimes an
error will appear (will link to uploaded stacktraces).

Workaround:
Wait until each validation attempt has finished before attempting validation
again.