akregator gui freezes for seconds every now and then

 Akregator freezes for around 5 seconds and does not respond at all.
This happens every half a minute, but it is random. It does not seem to be related with a given
action. This bug makes the use of it very annoying.
 I have around 150 sources with 5000 messages in total. I have attached gdb to it when it freezes and produced
a stack trace that I attach. I have also profiled akregator with oprofile to show the functions that hog the CPU.
This are the first lines output from opreport -a --symbols -m all:
samples cum. samples % cum. % app name symbol name
31930 31930 42.4595 42.4595 no-vmlinux /no-vmlinux
8221 40151 10.9320 53.3916 libQtCore.so.4.5.3 QRegExpMatchState::matchHere()
6593 46744 8.7672 62.1587 oprofiled /usr/bin/oprofiled
4463 51207 5.9348 68.0935 libc-2.10.2.so memcpy
1894 53101 2.5186 70.6121 nv_drv.so /usr/lib/xorg/modules/drivers/nv_drv.so
1694 54795 2.2526 72.8647 libQtCore.so.4.5.3 QChar::toLower() const
1675 56470 2.2274 75.0921 libz.so.1.2.3.3 /usr/lib/libz.so.1.2.3.3
1579 58049 2.0997 77.1918 libQtCore.so.4.5.3 QRegExpCharClass::in(QChar) const
1431 59480 1.9029 79.0947 libpixman-1.so.0.16.2 /usr/lib/libpixman-1.so.0.16.2
1342 60822 1.7846 80.8792 Xorg /usr/bin/Xorg
888 61710 1.1808 82.0601 libQtCore.so.4.5.3 QChar::toUpper() const
662 62372 0.8803 82.9404 libQtCore.so.4.5.3 __i686.get_pc_thunk.bx

Thanks!