Pulled the nely installed Ram, same problem. After boot can not get into system properties, internet or Outlook for 15 minutes. During that time I can open documents and other applications that I use like Paperport. After the 15 minutes it runs fine and in the system properties it shows either 2 or 3gb of Ram. Understand before adding this stick my computer would boot in less that a minute and I was off and running to any application and the internet.
You asked about the ram:
First two bays closest to the fan: 512 mb pc2 4200 533 mhz, came with Acer Aspire T180 so I don't know the brand.
Third Bay: Us Modular 1gb, pc2 4200 533 mhz(loaded this 3 years ago with no problems)
Forth Bay: Installed PNY 1 gb pc2 5300 533 mhz two days ago and as mentioned called PNY and they said I should use matching so last night I installed the pc2 4200 533 mhz.
In case you are wondering, I was never told that I should match brands so I pretty much bought the cheapest I could find within the pc2 4200 533 mhz category.
Please help. Thank you. Frank