Recently I have had a problem where my computer will freeze completely but if I happen to be streaming Pandora in a tab that will continue playing. If I wait about 2-5 minutes it will eventually come back and start working normally. I also noticed that during the period that it is unresponsive that the HDD activity light stays lit the whole time, not flashing.

I've ran memtest86+ and a diagnostic from Western Digital for my HDD model and none of them reported any errors. The specs for my computer are

1 x ASRock H55M/USB3 R2.0 LGA 1156 Intel H55 HDMI USB 3.0 Micro ATX Intel Motherboard
1 x CORSAIR Enthusiast Series CMPSU-550VX 550W ATX12V V2.2 SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply
1 x Intel Core i3-540 Clarkdale 3.06GHz LGA 1156 73W Dual-Core Desktop Processor Intel HD Graphics BX80616I3540
1 x G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Dual Channel Kit Desktop Memory Model F3-12800CL9D-4GBNQ
1 x ASUS PCE-N13 PCI Express 150/300Mbps Transfer/Receive Rate Wireless Adapter
1 x EVGA 01G-P3-1556-KR GeForce GTX 550 Ti (Fermi) FPB 1GB 192-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card

I can't imagine what would be causing these problems.