Yes blocking is present all the time when I open search tab.
Unfortunately there are no any command line option to enable detailed debug mode. After reproducing I have no any strangeness in output.  
[sirius@reactor]:~$ linuxdcpp
Loading: Hash database
Loading: Shared Files
Loading: Download Queue
About versions:
[sirius@reactor]:~$ ldd /usr/bin/linuxdcpp
        linux-vdso.so.1 =>  (0x00007fff6c2d1000)
        libpthread.so.0 => /lib/libpthread.so.0 (0x00007fcbb48f2000)
        libz.so.1 => /lib/libz.so.1 (0x00007fcbb46db000)            
        libbz2.so.1.0 => /lib/libbz2.so.1.0 (0x00007fcbb44ca000)    
        libcrypto.so.0.9.8 => /lib/libcrypto.so.0.9.8 (0x00007fcbb4143000)
        libssl.so.0.9.8 => /lib/libssl.so.0.9.8 (0x00007fcbb3ef5000)      
        libglade-2.0.so.0 => /usr/lib/libglade-2.0.so.0 (0x00007fcbb3cdc000)
        libgtk-x11-2.0.so.0 => /usr/lib/libgtk-x11-2.0.so.0 (0x00007fcbb36d1000)
        libgdk-x11-2.0.so.0 => /usr/lib/libgdk-x11-2.0.so.0 (0x00007fcbb3425000)
        libgdk_pixbuf-2.0.so.0 => /usr/lib/libgdk_pixbuf-2.0.so.0 (0x00007fcbb3209000)
        libpango-1.0.so.0 => /usr/lib/libpango-1.0.so.0 (0x00007fcbb2fc0000)          
        libgobject-2.0.so.0 => /usr/lib/libgobject-2.0.so.0 (0x00007fcbb2d7a000)      
        libgthread-2.0.so.0 => /usr/lib/libgthread-2.0.so.0 (0x00007fcbb2b75000)      
        libglib-2.0.so.0 => /lib/libglib-2.0.so.0 (0x00007fcbb28ae000)
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00007fcbb259e000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x00007fcbb2383000)
        libc.so.6 => /lib/libc.so.6 (0x00007fcbb2014000)
        /lib64/ld-linux-x86-64.so.2 (0x00007fcbb4b0e000)
        libdl.so.2 => /lib/libdl.so.2 (0x00007fcbb1e10000)
        libxml2.so.2 => /usr/lib/libxml2.so.2 (0x00007fcbb1ac3000)
        libatk-1.0.so.0 => /usr/lib/libatk-1.0.so.0 (0x00007fcbb18a3000)
        libpangoft2-1.0.so.0 => /usr/lib/libpangoft2-1.0.so.0 (0x00007fcbb167a000)
        libm.so.6 => /lib/libm.so.6 (0x00007fcbb13f6000)
        libpangocairo-1.0.so.0 => /usr/lib/libpangocairo-1.0.so.0 (0x00007fcbb11ea000)
        libgio-2.0.so.0 => /usr/lib/libgio-2.0.so.0 (0x00007fcbb0f41000)
        libcairo.so.2 => /usr/lib/libcairo.so.2 (0x00007fcbb0cbe000)
        libfreetype.so.6 => /usr/lib/libfreetype.so.6 (0x00007fcbb0a39000)
        libfontconfig.so.1 => /usr/lib/libfontconfig.so.1 (0x00007fcbb0807000)
        libgmodule-2.0.so.0 => /usr/lib/libgmodule-2.0.so.0 (0x00007fcbb0603000)
        libX11.so.6 => /usr/lib/libX11.so.6 (0x00007fcbb02cd000)
        libXcomposite.so.1 => /usr/lib/libXcomposite.so.1 (0x00007fcbb00ca000)
        libXdamage.so.1 => /usr/lib/libXdamage.so.1 (0x00007fcbafec8000)
        libXfixes.so.3 => /usr/lib/libXfixes.so.3 (0x00007fcbafcc2000)
        libXext.so.6 => /usr/lib/libXext.so.6 (0x00007fcbafab0000)
        libXrender.so.1 => /usr/lib/libXrender.so.1 (0x00007fcbaf8a6000)
        libXinerama.so.1 => /usr/lib/libXinerama.so.1 (0x00007fcbaf6a4000)
        libXi.so.6 => /usr/lib/libXi.so.6 (0x00007fcbaf499000)
        libXrandr.so.2 => /usr/lib/libXrandr.so.2 (0x00007fcbaf290000)
        libXcursor.so.1 => /usr/lib/libXcursor.so.1 (0x00007fcbaf086000)
        libpcre.so.3 => /lib/libpcre.so.3 (0x00007fcbaee56000)
        librt.so.1 => /lib/librt.so.1 (0x00007fcbaec4e000)
        libresolv.so.2 => /lib/libresolv.so.2 (0x00007fcbaea35000)
        libselinux.so.1 => /lib/libselinux.so.1 (0x00007fcbae817000)
        libpixman-1.so.0 => /usr/lib/libpixman-1.so.0 (0x00007fcbae5d2000)
        libdirectfb-1.2.so.0 => /usr/lib/libdirectfb-1.2.so.0 (0x00007fcbae347000)
        libfusion-1.2.so.0 => /usr/lib/libfusion-1.2.so.0 (0x00007fcbae13d000)
        libdirect-1.2.so.0 => /usr/lib/libdirect-1.2.so.0 (0x00007fcbadf22000)
        libpng12.so.0 => /usr/lib/libpng12.so.0 (0x00007fcbadcfb000)
        libxcb-render-util.so.0 => /usr/lib/libxcb-render-util.so.0 (0x00007fcbadaf7000)
        libxcb-render.so.0 => /usr/lib/libxcb-render.so.0 (0x00007fcbad8ee000)
        libxcb.so.1 => /usr/lib/libxcb.so.1 (0x00007fcbad6d2000)
        libexpat.so.1 => /lib/libexpat.so.1 (0x00007fcbad4a9000)
        libXau.so.6 => /usr/lib/libXau.so.6 (0x00007fcbad2a6000)
        libXdmcp.so.6 => /usr/lib/libXdmcp.so.6 (0x00007fcbad0a1000)