[SOLVED] RM UNUK - compiling error - .lock

Hello everyone,
I have just switched to Rapdiminer Unuk and I have some problems with compilation.

At first I would like to say:
- compilation with RM Vega was OK
- the problem was repeated on 2 independent computers
- the error is not related to java code (it seems that the problem lies in ANT RapidMiner_Unuk\build_extension.xml file)

The reported compiling error is:

BUILD FAILED
C:\workspaceRMUnuk\RapidMiner_Unuk\build_extension.xml:129: The following error occurred while executing this line:
C:\workspaceRMUnuk\RapidMiner_Unuk\build_extension.xml:181: The following error occurred while executing this line:
C:\workspaceRMUnuk\RapidMiner_Unuk\build_extension.xml:186: The following error occurred while executing this line:
Error reading project file C:\workspaceRMUnuk\.metadata\.lock: Process cannot work with file, or other process locked part of this file.

The problem is in particular in:
(RapidMiner_Unuk\build_extension.xml:129)
<antcall target="build.dependencies" />

(RapidMiner_Unuk\build_extension.xml:181)

<for param="buildfile">
			<path>
				<union refid="build.dependentExtensions.actual" />
			</path>
			<sequential>
				<ant antfile="@{buildfile}" target="install" inheritall="false" useNativeBasedir="true" />
			</sequential>
		</for>

(RapidMiner_Unuk\build_extension.xml:186)

  <ant antfile="@{buildfile}" target="install" inheritall="false" useNativeBasedir="true" />

The problem seem to be that the "FOR" cyclus tries to iterate over each file in the workspace. Any help would be really appreciated.

Best,
Radim Burget