Before loading Magento extension files, please:
1. Navigate to Magento Admin panel >System > Configuration > Developer Tab and disable "Merge css / js". We suggest that you enable error reporting.
2. Then navigate to Magento Admin panel > System > Cache Storage Management and and disable Cache.
3. Be sure that the Compilation Сode is disabled (Magento Admin panel > System > Tools > Compilation)
Also be sure that you set the memory_limit = 512M or more to make Magento work properly