Sometimes Spinning ball since RAM upgrade

Question

i ordered 1GB RAM and replaced it with the 512MB.
since then i get a spinning ball sometimes, but only if i do several tasks at once.
like using Photoshop, Indesign, Mail, Safari, Itunes and dashboard and finder same time intensively. the ball doesnt stop. it lasts for hours.
and everything is terrible slow or more frozen. i have to reset the pb then with applectrlturnonbutton as the "turn-off" task in the finder isnt working anymore.
before (with 1.5GB RAM) i did all these intense actions too, and nothing special happened, only the fan raised and everything seemed to be a bit slower. but never mind. i never ever saw the spinning ball in the finder happen so long, only for 1 or 2 seconds, yes, but never for minutes or hours...
now with 2GB, i get a spinning ball sometimes when using it heavily.
the funny thing is, i ordered it at the company i use to order RAM for Apple since 5 years. http://www.dsp-memory.de/v1/catalog/ and everybody in germany is ordering there, as it is good quality with fine prices and dedicated for Apple only (no PC-RAM for sure)
i didnt add anyting else in the last 2 weeks, than the 1GB RAM and a PCMCIA card from formac "watchandgo" dbv-t for TV, but its not in the powerboook, only at night for watching TV and it works fine. before the 2 weeks i never had any problem or reset happen here...
how can i test the RAM and rule it out or define the problem?
"about my mac" says proper infos:
1. SODIMM0/J20STANDARD:
Größe: 1 GB
Typ: DDR2 SDRAM
Geschwindigkeit: PC2-4200S-444
Status: OK
2. SODIMM1/J23REVERSED:
Größe: 1 GB
Typ: DDR2 SDRAM
Geschwindigkeit: PC2-4200S-444
Status: OK
is there any application out there wich can test the RAM and then says "works 100% fin"e or simple "not fine" ?
thanks!"

Answer 1

One application to test memory is memtest, which can be found at http://www.memtestosx.org/ If you want a GUI front end to memtest, you can use rember, which can be found at http://www.kelleycomputing.net:16080/rember/ Unless running it once turns up a problem, I'd probably let the test run multiple times overnight.
Have you looked at your memory usage under the activity monitor? The Apple note describing how the memory is used is at http://docs.info.apple.com/article.html?artnum=107918 This may give you some insights. Also of interest would be page in/page outs with the increased memory (if all is working as expected, you'd expect page outs to be low, preferably non-existant!)