I cannot reproduce this on Domino 9.0.1 server with Extlib 901v00_04.20140226-1506 installed (that is Extlib 901 v4 release). Are you sure you are running a 9.0.1 server?
com.ibm.xsp.extlib.renderkit.html_extended.layout.AbstractApplicationLayoutRenderer.writeSearchBox(AbstractApplicationLayoutRenderer.java:798)
is attempting to call:
com/ibm/xsp/util/JSUtil.addSingleQuoteString(java/lang/StringBuilder,java/lang/String)`
but it is finding that the addSingleQuoteString method does not exist.
addSingleQuoteString was added to JSUtil in 9.0.1. If you're seeing a NoSuchMethodError, it implies that your server is running 9.0 or an earlier Domino version.Specifically, it implies that this extsn plugin is not at version 9.0.1:
C:Domino\osgi\shared\eclipse\plugins\com.ibm.xsp.extsn_9.0.1.20130919-1200\
Can you run the following commands in your domino console, and post the output?
show server
tell htttp osgi ss com.ibm.xsp.extlib