Here's a bit of information about what high resource usage really is:
http://x10hosting.com/wiki/High_Resource_Usage
Short version: your script is using too much CPU when executing. You would have to take a look at the script, disabling plugins/addons that are not needed and that could be resource intensive (sitemap generators can be rather resource intensive for instance, as can other automated tasks).
Fetching content from outside sources can cause script execution to take long enough for cpu usage to go over the limits.
Your account may not use more then 25% of one CPU (short bursts are ok). It may further more not utilize the CPU for more then 240 seconds total per hour, long execution times can easily trigger this part.
Correctly configured cache function would help lowering execution times, and make the site load faster.
On the last suspension your account had 8 concurrent php processes running, together they used up:
Sun 24 Jul 2011 06:29:29 / 1311503369:
cpu: 28.600
mem: 3.200
ctm: 00:00:03
The account is at that point a little over the limit for CPU, and rather close to the limits of memory as well.
