Cannot edit audio nodes

I am finding it impossible to edit some audio nodes. There are two issues, this first is that something times out after 30 seconds when I submit the edit, and I get an error message referencing different lines in module.audio.mp3.php.

The second is that sometimes when I attempt to submit the edit, I get a page not found

I was running version 0.3, but when I ran into the first issue, I upgraded to 1.4. Now I still get the first issue, but often the second as well. The only relevant line I can find in module.audio.mp3.php is:

1209- $previousvalidframe = $ThisFileInfo['avdataoffset'];
1210- while (ftell($fd) < $ThisFileInfo['avdataend']) {
1211: set_time_limit(30);
1212- $head4 = fread($fd, 4);
1213- if (strlen($head4) < 4) {
1214- break;

I've tried changing the timeout to larger values, but without success. Finally, it seems to be file and/or node dependent. I can edit certain nodes, but not others. Most of my files are quite large, but I have smaller files which don't work, and larger ones which do.