Latency Problem all of the sudden

[robotboy]

I recently started a new project, and all of the sudden I have issues with latency. I laid down a MIDI drum track and then overdubbed electric guitar--straight, no plug-ins. Used all of the settings I have always used for years--256 buffer, 6 processors, no delay compensation. But before I even start recording, the guitar signal keeps dropping out. I tried to record anyway (it doesn't drop out during recording), but the latency is very noticeable. The drop outs go away if I increase buffer size, but 256 is already pushing it in terms of being on beat.

The only change I made recently was an install of EZ Drummer. But the problem persists even if I use my old BFD plug in.

I have read lots of threads on this, but can't find a solution. I trashed prefs, etc. But nothing has worked. Could it be my external hard drive crapping out? It does have some miles on it.

Can anyone help me? Thanks