Good signal strength but very high packet loss occasionally

I have a Linksys WRT150N router with DD-WRT firmware on it. It works fine for most of the day but occasionally (once or twice a day) my connection will become extremely slow. When this happens, I usually can't even access the router via its IP wirelessly. The ping to the router becomes extremely high and there is a >40% packet loss. Rebooting the router does not help (atleast not immediately) and the problem resolves itself spontaneously after 10-20 minutes.
Additional info:
-There is a 5.8 ghz phone nearby (router is 2.4ghz) but otherwise there are no sources of interference.
-Wired connection works fine while the wireless is experiencing this problem.
-The problem occurs simultaneously on all computers.
-The problem is independent of usage load and time of the day.
-I'm using N-mode only. Changing channels does not help.
-This is what the ping looks like:

Pinging 192.168.128.1 with 32 bytes of data:
Reply from 192.168.128.1: bytes=32 time=260ms TTL=64
Reply from 192.168.128.1: bytes=32 time=1227ms TTL=64
Reply from 192.168.128.1: bytes=32 time=1929ms TTL=64
Reply from 192.168.128.1: bytes=32 time=41ms TTL=64
Reply from 192.168.128.1: bytes=32 time=1000ms TTL=64
Request timed out.
Request timed out.
Request timed out.
Reply from 192.168.128.1: bytes=32 time=1547ms TTL=64
Request timed out.
Reply from 192.168.128.1: bytes=32 time=3ms TTL=64
Reply from 192.168.128.1: bytes=32 time=987ms TTL=64
Reply from 192.168.128.1: bytes=32 time=2ms TTL=64
Request timed out.
Reply from 192.168.128.1: bytes=32 time=29ms TTL=64
Request timed out.
Request timed out.
Request timed out.

Ping statistics for 192.168.128.1:
Packets: Sent = 18, Received = 10, Lost = 8 (44% loss),
Approximate round trip times in milli-seconds:
Minimum = 2ms, Maximum = 1929ms, Average = 702ms

I performed a hard reset on the router and that seems to have fixed the issue for now. I'm hoping that it doesn't come back. But if it does then I'll be sure to post again.