I have made next changes to solve this problem (patched files are in attachment): 
 
file client\WebServerManager.cpp 
line 105. 
original: 
pagehtml += "           <meta http-equiv='Content-Type' content='text/html; charset=windows-1250' />"; 
 
replacement: 
pagehtml += "		<meta http-equiv='Content-Type' content='text/html; charset=utf-8' />"; 
 
line 115. 
original: 
pagehtml += "               <form method='get' action='index.htm' enctype='multipart/form-data'>"; 
 
replacement: 
pagehtml += "		<form method='get' action='index.htm'>"; 
 
comment: incorrect enctype for this purpose, using default. 
 
line 145. 
original: 
pagehtml += "        <meta http-equiv='Content-Type' content='text/html; charset=windows-1250' />"; 
 
replacement: 
pagehtml += "	 <meta http-equiv='Content-Type' content='text/html; charset=utf-8' />"; 
 
line 349. 
original: 
        string ret = "<form method='GET' name='search' ACTION='search.html' enctype='multipart/form-data'>"; 
 
replacement: 
string ret = "<form method='GET' name='search' ACTION='search.html'>"; 
 
line 383. 
original: 
ret += "<option value='8'>TTH"; 
 
replacement: 
ret += "<option value='8'>TTH</select>"; 
 
comment: the <select> tag must be closed. 
 
line 536. 
original: 
QueueManager::getInstance()->add(m["name"],Util::toInt64(m["size"]),m["tth"]); 
 
replacement: 
	QueueManager::getInstance()->add(Util::encodeURI(m["name"], true),Util::toInt64(m["size"]),m["tth"]); 
	 
comment: decoding "name"'s value. 
 
line 546. 
original: 
                                        toSend = Text::utf8ToAcp(WebServerManager::getInstance()->getPage(header, IP)); 
 
replacement: 
toSend = /* Text::utf8ToAcp */(WebServerManager::getInstance()->getPage(header, IP)); 
 
comment: recode operation is not required. 
 
file client\WebServerManager.h 
line 145. 
original: 
int i = 0; 
while( (i = search_str.find("+", i)) != string::npos) { 
search_str.replace(i, 1, " "); 
i++; 
} 
 
replacement: 
/* 
int i = 0; 
while( (i = search_str.find("+", i)) != string::npos) { 
search_str.replace(i, 1, " "); 
i++; 
} 
*/ 
search_str=Util::encodeURI(search_str, true); 
 
comment: search request must be decoded. client.zip