Magento: Import products freezing (only imports few products at a time)

Hello, Since we upgraded our magento I have been unable to successfully import products via the import/export dataflow option in magento. At the moment I upload my csv and it may have processed say 10 out if 700 products then freezes, process icon is still animated but the overall records imported text does not increase. When I check the manage product catalog section in magento backend, it shows the 10 which have been imported, so it has clearly worked but just hasn't gone any further. I have read up on how to fix this like trying different csv's or changing the php memory file size but not sure how to do the latter. In magento before I upload via dataflow it states; Your server PHP settings allow you to upload files not more than 8M at a time. Please modify post_max_size (currently is 8M) and upload_max_filesize (currently is 99M) values in [login to view URL] if you want to upload larger files. My file sizes are only ever 500k to 1mb so it should work. I require this problem to be fixed so I can upload 1000 products at a time (like I used to be able to). Thanks Lewis