xwiki invalid character question

Hi, I sometimes get the following error in xwiki (0.9.840) when I try to browse a category (e.g. KidsCorner in the following). It is related to some invalid characters in the wiki content but I usually paste some useful content into our wiki and don't know what character is forbiddern. Is there a way for us to avoid problem like the following. It made all the pages in the category not browsable and is very inconvenient. Now what I have to do is to manually go to the postgresql database to modify some table content and it doesn't always work. Have you guys encountered similar problem and is there a better solution to fix/avoid it? Thanks -Jimmy ================================================================ Error number 4001 in 4: Error while parsing velocity page Blog.Category Wrapped Exception: Invocation of method 'getDocument' in class com.xpn.xwiki.api.XWiki threw exception class com.xpn.xwiki.XWikiException : Error number 3202 in 3: Exception while reading document Main.KidsCorner Wrapped Exception: Exception occurred inside setter of com.xpn.xwiki.doc.XWikiDocument.archive Error number 4001 in 4: Error while parsing velocity page Blog.Category Wrapped Exception: Invocation of method 'getDocument' in class com.xpn.xwiki.api.XWiki threw exception class com.xpn.xwiki.XWikiException : Error number 3202 in 3: Exception while reading document Main.KidsCorner Wrapped Exception: Exception occurred inside setter of com.xpn.xwiki.doc.XWikiDocument.archive com.xpn.xwiki.XWikiException: Error number 4001 in 4: Error while parsing velocity page Blog.Category Wrapped Exception: Invocation of method 'getDocument' in class com.xpn.xwiki.api.XWiki threw exception class com.xpn.xwiki.XWikiException : Error number 3202 in 3: Exception while reading document Main.KidsCorner Wrapped Exception: Exception occurred inside setter of com.xpn.xwiki.doc.XWikiDocument.archive at com.xpn.xwiki.render.XWikiVelocityRenderer.evaluate(XWikiVelocityRenderer.java:131) at com.xpn.xwiki.render.XWikiVelocityRenderer.render(XWikiVelocityRenderer.java:87) at com.xpn.xwiki.render.XWikiRenderingEngine.renderText(XWikiRenderingEngine.java:116) at com.xpn.xwiki.XWiki.include(XWiki.java:1937) at com.xpn.xwiki.api.XWiki.includeForm(XWiki.java:463) at com.xpn.xwiki.api.XWiki.includeForm(XWiki.java:451) at sun.reflect.GeneratedMethodAccessor306.invoke(Unknown Source) ... Caused by: org.apache.commons.jrcs.rcs.TokenMgrError: Lexical error at line 128, column 18. Encountered: "u7b4b" (31563), after : "@ http://afgbabyfuniture.com http://www.altababyweb.com http://www.bassettbaby.com n convertable cribs http://www.bonavita-cribs.comn Stroller: n* http://www.toysrus.com/product/index.jsp?productId=2266773&amp;cp=22559… http://store.babycenter.com/product/gear/strollers/travel_systems//7934?sta… http://store.babycenter.com/category/gear/strollers/lightweight_strollers/?… Preganency Symptomsn [Muscle Cramp(u62bd" at org.apache.commons.jrcs.rcs.ArchiveParserTokenManager.getNextToken(ArchiveParserTokenManager.java:800) at org.apache.commons.jrcs.rcs.ArchiveParser.jj_consume_token(ArchiveParser.java:558) at org.apache.commons.jrcs.rcs.ArchiveParser.string(ArchiveParser.java:506) at org.apache.commons.jrcs.rcs.ArchiveParser.text(ArchiveParser.java:430) at org.apache.commons.jrcs.rcs.ArchiveParser.archive(ArchiveParser.java:102) at org.apache.commons.jrcs.rcs.ArchiveParser.load(ArchiveParser.java:55) at org.apache.commons.jrcs.rcs.Archive.<init>(Archive.java:230) at com.xpn.xwiki.doc.XWikiDocument.setArchive(XWikiDocument.java:475) … 122 more