Only too normal. Its spirogyra. Snails and young tadpoles eat it enthusiastically. I think its encouraged when there are lots of nutrients in the water. If its only on your weed don't worry about it but make sure you have enough ramshorn snails. If it spreads into the rest of the pond you can wind it round sticks and pull it out if there isn't too much.
For info about using barley straw to control it put Barley Straw Ponds into Google for lots of info on using this remedy.

once the nutrients balance out the algae will die off. When you say pond weed do you mean the oxygenators? They will quickly out grow the problem.From first seeing it to it clearing is usually about 6 weeks. the speed at which it goes is amazing 2 days often.

Talking of oxygenators, have a look at your green filaments on a bright sunny day and you might see little bubbles of oxygen on them. SBG when you say clearing are you referring to green water? We used to find that spirogyra helped to keep the water clear as long as it didn't go mad (which it very easily does if there isn't enough pond weed.)

I call this condition blanket weed and it is at its worse in the early spring before water temperatures allow barley straw and pond plants become effective in removing nutrients from the water to slow its growth down. During this time it will form a green membrane covering everything. For me the only effective solution is to make a blanket weed remover as follows: take a round toilet brush and securely tape its handle to a mop stick. Wait till the full sun is shining on the pond surface which will make the bubbles in the weed cause the membrane to rise to the surface. Stick the round brush into the blanket and turn clockwise which will catch and spin the weed around the . like linguini around a fork. Remove this heavy lump caught around the brush from the water and unravel it from the brush in a counterclockwise manner. Do it slowly to examine it as you go along to remove small fish, snails and tadpoles from this weed. Do this mechanical control of blanket weed every week. To wait for the biological controls to take effect might result in what would be an avoidable mess in your pond

That's ingenious!

I forgot to mention that on the other end of the mop stick tape a medium size fine mesh fish net. This makes a great pond skimmer which can remove floating debris from the pond surface.