Hi there,
wow so your suffer from stupid doctors too then?
I too have some stupid dopes as doctors at my local hospital, they dont even know what a shunt is, several times i had 'suspected shunt failures' they just stuck me in a room to be observed instead of getting me an emergency CT scan.
The time my shunt did malfunction, i displayed exactly the same symptoms as what i had before, but luckily i just happened to be at my specialist hospital at the time whilst having an icp monitoring.

I had my shunt fully revised in september 2008.
When i got really ill in hospital, i first experienced a shunt pain, felt like a gripping pain around my shunt area on my head. i had never felt this before, was moments later that i went comatose and had an emergency revision.
My valve was changed from low pressure to high pressure in that operation.
Since that operation, i have been experiencing this pain again and again, it started off being about once every 2 weeks and then gradually got more frequent, well all of a sudden actually. A week ago, i was getting this pain about once twice a week, but since the day before last, i must of experienced this pain over 50 times!! Its become very strong now too, went from me twtiching my face when it happens to me now scrunching up my face and flinches when it comes. Its intermittant, will last as fast as a thump, then go but then comes back out of the blue.

I really dont understand what this pain is, im also experiencing lightheadedness upon rising aswell as my eyes blacking out for a few seconds. I must say, i dont tend to get these thumpoing pains when im lying flat, i get them whilst upright or when my neck is propped up with a pillow, perhaps at a 60 degree angle.

Im wondering about whether its overdrainage.
symptoms of that, or so ive looked up, says...
dizziness
headache
fainting/ blacking out.

I was in hospital last week to have my shunt converted to a VA shunt due to abdominal pain from the catheter, i went through every problem ive experienced with this valve, my NS assistant wanted to revise the whole shunt because it sounded like i was overdraining.
But after waking up from the operation, my tube had just been diverted to my heart and the valve hadnt been changed.

...The only thing that the conversion has helped with, is the abdominal pain...the other problems still exist, im thinking its this damn valve, the low pressure valve, i suffered with for 12 years with no problems...i think this was right for me. But since they changed it to a high pressure valve, ive had nothing but problems :/

Hope you find out whats going on soon
Good luck